dissolve app/ into repo root (D-056)

Single Flutter package at the repo root. All code, tests, assets,
and platform directories moved from app/ to root. Package renamed
from clide_app to clide — all imports rewritten. Merged pubspec
combines core (ffi) and app (flutter, yaml, xterm) dependencies.
Makefile simplified: no APP_PRESENT conditionals, no cd, no daemon
lifecycle. 317 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/extension/src/contribution.dart

@@ -0,0 +1,157 @@
+import 'package:clide/clide.dart';
+import 'package:clide/kernel/src/panels/slot_id.dart';
+import 'package:flutter/widgets.dart';
+
+/// One atom contributed by a [ClideExtension]. Extensions declare N of
+/// these in a manifest; the kernel and slot hosts render them.
+///
+/// Adding a new contribution type: add a case to this sealed hierarchy,
+/// extend the host dispatch in the default-layout extension, and bump
+/// the extension manifest schema version.
+sealed class ContributionPoint {
+  const ContributionPoint({required this.id});
+
+  /// Stable id for this contribution, unique within its extension.
+  final String id;
+
+  /// The slot this contribution targets, or `null` for non-slot
+  /// contributions (commands, events, grammars).
+  SlotId? get slot => null;
+}
+
+/// A tab in a slot that hosts tabs (sidebar / workspace / context).
+class TabContribution extends ContributionPoint {
+  const TabContribution({
+    required super.id,
+    required this.slot,
+    required this.title,
+    required this.build,
+    this.icon,
+    this.priority = 0,
+    this.fileGlobs = const [],
+    this.listenable,
+    this.titleKey,
+    this.i18nNamespace,
+  });
+
+  @override
+  final SlotId slot;
+  final String title;
+  final WidgetBuilder build;
+  final Object? icon;
+  final int priority;
+  final List<String> fileGlobs;
+  final Listenable? listenable;
+
+  /// When set, the slot host resolves the display title via
+  /// `i18n.string(titleKey, namespace: i18nNamespace, placeholder: title)`.
+  /// [title] stays as the English fallback (also used in tests/logs).
+  final String? titleKey;
+
+  /// The i18n namespace to look up [titleKey] in. Extensions usually
+  /// pass their own `id`. Required when [titleKey] is set.
+  final String? i18nNamespace;
+}
+
+/// A status-bar item. Order is determined by [priority] within each
+/// alignment group; negative priorities float left, positive right.
+class StatusItemContribution extends ContributionPoint {
+  const StatusItemContribution({
+    required super.id,
+    required this.build,
+    this.priority = 0,
+    this.listenable,
+  });
+
+  @override
+  SlotId get slot => Slots.statusbar;
+  final WidgetBuilder build;
+  final int priority;
+  final Listenable? listenable;
+}
+
+/// A button in the main toolbar.
+class ToolbarButtonContribution extends ContributionPoint {
+  const ToolbarButtonContribution({
+    required super.id,
+    required this.label,
+    required this.onPressed,
+    this.icon,
+    this.tooltip,
+    this.priority = 0,
+  });
+
+  @override
+  SlotId get slot => Slots.toolbar;
+  final String label;
+  final Object? icon;
+  final String? tooltip;
+  final int priority;
+  final VoidCallback onPressed;
+}
+
+/// A command extensions register with [CommandRegistry]. Surfaced by the
+/// command palette, the keybinding resolver, and `clide` CLI subcommands.
+class CommandContribution extends ContributionPoint {
+  const CommandContribution({
+    required super.id,
+    required this.command,
+    required this.run,
+    this.title,
+    this.defaultBinding,
+  });
+
+  final String command; // e.g. "git.commit"
+  final String? title; // "Git: Commit staged"
+  final String? defaultBinding; // e.g. "ctrl+shift+g"
+  final Future<IpcResponse> Function(List<String> args) run;
+}
+
+/// Registers an item in the OS tray / menu-bar.
+class TrayItemContribution extends ContributionPoint {
+  const TrayItemContribution({
+    required super.id,
+    required this.label,
+    required this.onSelected,
+    this.priority = 0,
+  });
+
+  @override
+  SlotId get slot => Slots.tray;
+  final String label;
+  final int priority;
+  final VoidCallback onSelected;
+}
+
+/// A named layout arrangement. One "classic" preset ships with
+/// `builtin.default-layout`; other presets can be contributed.
+class LayoutPresetContribution extends ContributionPoint {
+  const LayoutPresetContribution({
+    required super.id,
+    required this.displayName,
+    required this.slots,
+  });
+
+  final String displayName;
+  final List<LayoutSlot> slots;
+}
+
+/// One slot in a [LayoutPresetContribution]. Describes where the slot
+/// appears and its initial size/visibility.
+class LayoutSlot {
+  const LayoutSlot({
+    required this.slot,
+    required this.position,
+    this.defaultSize,
+    this.minSize,
+    this.maxSize,
+    this.visible = true,
+  });
+
+  final SlotId slot;
+  final SlotPosition position;
+  final double? defaultSize;
+  final double? minSize;
+  final double? maxSize;
+  final bool visible;
+}

lib/extension/src/extension.dart

@@ -0,0 +1,96 @@
+import 'package:clide/extension/src/contribution.dart';
+import 'package:clide/kernel/src/clipboard.dart';
+import 'package:clide/kernel/src/commands/palette.dart';
+import 'package:clide/kernel/src/commands/registry.dart';
+import 'package:clide/kernel/src/dialog.dart';
+import 'package:clide/kernel/src/events/bus.dart';
+import 'package:clide/kernel/src/files.dart';
+import 'package:clide/kernel/src/focus.dart';
+import 'package:clide/kernel/src/i18n/i18n.dart';
+import 'package:clide/kernel/src/ipc/client.dart';
+import 'package:clide/kernel/src/log.dart';
+import 'package:clide/kernel/src/net.dart';
+import 'package:clide/kernel/src/notify.dart';
+import 'package:clide/kernel/src/os.dart';
+import 'package:clide/kernel/src/panels/arrangement.dart';
+import 'package:clide/kernel/src/panels/registry.dart';
+import 'package:clide/kernel/src/project.dart';
+import 'package:clide/kernel/src/secrets.dart';
+import 'package:clide/kernel/src/settings.dart';
+import 'package:clide/kernel/src/theme/controller.dart';
+import 'package:clide/kernel/src/tray.dart';
+
+/// One shipping unit. Built-in extensions compile in as Dart subclasses;
+/// third-party extensions run as Lua scripts wrapped by a `LuaExtension`
+/// adapter (Tier 6).
+abstract class ClideExtension {
+  String get id;
+  String get title;
+  String get version;
+
+  /// IDs of other extensions that must be activated before this one.
+  /// Missing deps → this extension is skipped at load with a warning.
+  List<String> get dependsOn => const [];
+
+  /// The atoms this extension contributes.
+  List<ContributionPoint> get contributions;
+
+  /// Called once after dependencies activate.
+  Future<void> activate(ClideExtensionContext ctx) async {}
+
+  /// Called when the extension is disabled or the app shuts down.
+  Future<void> deactivate() async {}
+}
+
+/// Handed to every [ClideExtension.activate]. Lists every kernel service
+/// an extension may reach. The extension manager constructs a concrete
+/// instance with refs; tests can pass fakes.
+///
+/// The interface deliberately lists services individually rather than
+/// exposing a `KernelServices` aggregate — doing so would create an
+/// import cycle between the kernel facade and this file.
+abstract class ClideExtensionContext {
+  String get id;
+
+  Logger get log;
+  EventBus get events;
+  SettingsStore get settings;
+  ThemeController get theme;
+  I18n get i18n;
+  PanelRegistry get panels;
+  LayoutArrangement get arrangement;
+  CommandRegistry get commands;
+  PaletteController get palette;
+  ClideClipboard get clipboard;
+  FileServices get files;
+  Notifications get notify;
+  DialogRouter get dialog;
+  TrayRegistry get tray;
+  SecretsVault get secrets;
+  OsBridge get os;
+  NetworkStatus get net;
+  FocusTracker get focus;
+  ProjectManager get project;
+  DaemonClient get ipc;
+}
+
+/// Sugar for i18n lookups scoped to this extension's namespace.
+extension ClideExtensionContextI18n on ClideExtensionContext {
+  /// `ctx.t('welcome.title', placeholder: 'clide')` →
+  /// `i18n.string('welcome.title', namespace: id, placeholder: 'clide')`.
+  String t(String key, {String? placeholder}) =>
+      i18n.string(key, namespace: id, placeholder: placeholder);
+
+  /// [t] with interpolation replacers.
+  String tr(
+    String key, {
+    String? placeholder,
+    List<I18nReplacer> replacers = const [],
+  }) =>
+      i18n.interpolated(
+        key,
+        namespace: id,
+        placeholder: placeholder,
+        replacers: replacers,
+      );
+}

lib/extension/src/host.dart

@@ -0,0 +1,36 @@
+import 'dart:io';
+
+import 'package:clide/extension/src/manifest.dart';
+
+/// Scans the third-party extensions root for `manifest.yaml` files.
+///
+/// Built-ins are registered by the app at boot; this scanner handles
+/// installed third-party extensions. Tier 0 returns an empty list
+/// until the Lua adapter lands — every call is safe to make anyway.
+class ExtensionScanner {
+  const ExtensionScanner();
+
+  /// Typical install root: `~/.clide/extensions/<id>/manifest.yaml`.
+  /// Override for tests.
+  Directory defaultRoot() {
+    final home = Platform.environment['HOME'] ?? '/tmp';
+    return Directory('$home/.clide/extensions');
+  }
+
+  Future<List<ExtensionManifest>> discover({Directory? root}) async {
+    final dir = root ?? defaultRoot();
+    if (!await dir.exists()) return const [];
+    final out = <ExtensionManifest>[];
+    await for (final entity in dir.list()) {
+      if (entity is! Directory) continue;
+      final m = File('${entity.path}/manifest.yaml');
+      if (!await m.exists()) continue;
+      try {
+        out.add(await ExtensionManifest.fromFile(m));
+      } on FormatException catch (_) {
+        // skip malformed manifests; the extensions-ui will surface them
+      }
+    }
+    return out;
+  }
+}

lib/extension/src/manifest.dart

@@ -0,0 +1,60 @@
+import 'dart:io';
+
+import 'package:yaml/yaml.dart';
+
+/// A parsed third-party extension manifest.
+///
+/// Built-in extensions don't need a manifest file — they compile in as
+/// Dart subclasses of [ClideExtension]. Third-party extensions ship a
+/// `manifest.yaml` under `~/.clide/extensions/<id>/` alongside their
+/// Lua entrypoint; this class parses and validates that file.
+class ExtensionManifest {
+  const ExtensionManifest({
+    required this.id,
+    required this.title,
+    required this.version,
+    required this.dependsOn,
+    required this.entry,
+    required this.schemaVersion,
+  });
+
+  final String id;
+  final String title;
+  final String version;
+  final List<String> dependsOn;
+  final String entry; // relative path to lua entrypoint
+  final int schemaVersion;
+
+  factory ExtensionManifest.fromYamlString(String text) {
+    final doc = loadYaml(text);
+    if (doc is! Map) {
+      throw const FormatException('manifest root is not a map');
+    }
+    final id = doc['id'];
+    if (id is! String || id.isEmpty) {
+      throw const FormatException('manifest missing `id`');
+    }
+    final title = (doc['title'] as String?) ?? id;
+    final version = (doc['version'] as String?) ?? '0.0.0';
+    final entry = (doc['entry'] as String?) ?? 'extension.lua';
+    final schemaVersion = (doc['schema_version'] as int?) ?? 1;
+    final depsYaml = doc['depends_on'];
+    final deps = <String>[];
+    if (depsYaml is YamlList) {
+      for (final d in depsYaml) {
+        if (d is String) deps.add(d);
+      }
+    }
+    return ExtensionManifest(
+      id: id,
+      title: title,
+      version: version,
+      dependsOn: deps,
+      entry: entry,
+      schemaVersion: schemaVersion,
+    );
+  }
+
+  static Future<ExtensionManifest> fromFile(File f) async =>
+      ExtensionManifest.fromYamlString(await f.readAsString());
+}