feat(settings): schema-driven settings engine (T-448)

The core of the settings panel (epic T-444). Subsystems describe a category
as data — a SettingsCategory of carded SettingsSections of SettingsFields
(toggle / select / text / number / opens-external-file), each bound to a
SettingsStore key with help text, a default, and reset-to-default.

Registration is declarative: a new SettingsCategoryContribution carries the
category; the extension manager routes it into a new kernel SettingsRegistry
(exposed on KernelServices), which the panel reads via ClideKernel. Adding a
category is now pure data + a contribution — no widget code.

SettingsCategoryView renders a category into carded sections per ui-design
surface.md: panelHeader card fill, dividerColor border, inputs receding to
panelBackground; select reuses the anchored-overlay menu, text/number commit
on Enter or blur (numeric clamps to bounds). The modal panel now shows the
selected/first registered category, falling back to the empty state.

Tests: registry (sort / dedup / notify), contribution routing on activation,
renderer (render + toggle/select write-through + reset), modal-with-category.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/kernel/src/extensions_manager.dart

@@ -25,6 +25,7 @@ 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/settings_registry.dart';
 import 'package:clide/kernel/src/theme/controller.dart';
 import 'package:clide/kernel/src/tray.dart';
 import 'package:flutter/foundation.dart';
@@ -55,6 +56,7 @@ class ExtensionManager extends ChangeNotifier {
     required this.focus,
     required this.project,
     required this.ipc,
+    required this.settingsRegistry,
   });
 
   final Logger log;
@@ -81,6 +83,7 @@ class ExtensionManager extends ChangeNotifier {
   final FocusTracker focus;
   final ProjectManager project;
   final DaemonClient ipc;
+  final SettingsRegistry settingsRegistry;
 
   final Map<String, ClideExtension> _known = {};
   final Set<String> _activated = {};
@@ -256,6 +259,9 @@ class ExtensionManager extends ChangeNotifier {
         // Presets are consumed by the default-layout extension in its
         // own activate(); nothing for the kernel to do here.
         break;
+      case SettingsCategoryContribution s:
+        // register() throws on a duplicate id, rolling activation back.
+        settingsRegistry.register(s.category);
     }
   }
 
@@ -276,6 +282,8 @@ class ExtensionManager extends ChangeNotifier {
         tray.remove(t.id);
       case LayoutPresetContribution _:
         break;
+      case SettingsCategoryContribution s:
+        settingsRegistry.unregister(s.category.id);
     }
   }
 

lib/kernel/src/facade.dart

@@ -34,6 +34,7 @@ import 'package:clide/kernel/src/recent_files.dart';
 import 'package:clide/kernel/src/scheduler.dart';
 import 'package:clide/kernel/src/secrets.dart';
 import 'package:clide/kernel/src/settings.dart';
+import 'package:clide/kernel/src/settings_registry.dart';
 import 'package:clide/kernel/src/theme/controller.dart';
 import 'package:clide/kernel/src/theme/loader.dart';
 import 'package:clide/kernel/src/toolchain.dart';
@@ -81,10 +82,14 @@ class KernelServices {
     required this.textZoom,
     required this.toast,
     required this.logRing,
+    required this.settingsRegistry,
   });
 
   final Logger log;
   final SettingsStore settings;
+
+  /// Categories registered for the Settings panel (T-444).
+  final SettingsRegistry settingsRegistry;
   final DaemonBus events;
   final MessageBus messages;
 
@@ -155,6 +160,7 @@ class KernelServices {
 
     final settings = SettingsStore(appDir: appDir, onError: (m) => log.warn('settings', m));
     await settings.load();
+    final settingsRegistry = SettingsRegistry();
 
     final i18n = I18n(loader: i18nLoader, log: log, defaultLocale: defaultLocale, initialLocale: initialLocale, availableLocales: availableLocales);
     for (final ns in preloadNamespaces) {
@@ -238,6 +244,7 @@ class KernelServices {
       focus: focus,
       project: project,
       ipc: ipc,
+      settingsRegistry: settingsRegistry,
     );
 
     if (autoStartDaemonClient) {
@@ -248,6 +255,7 @@ class KernelServices {
       log: log,
       logRing: logRing,
       settings: settings,
+      settingsRegistry: settingsRegistry,
       events: events,
       messages: messages,
       filterStates: filterStates,
@@ -287,6 +295,7 @@ class KernelServices {
     await ipc.stop();
     ipc.dispose();
     settings.dispose();
+    settingsRegistry.dispose();
     theme.dispose();
     panels.dispose();
     arrangement.dispose();

lib/kernel/src/settings_registry.dart

@@ -0,0 +1,37 @@
+import 'package:clide/kernel/src/settings_schema.dart';
+import 'package:flutter/foundation.dart';
+
+/// Holds the [SettingsCategory] schemas subsystems register against the kernel
+/// (via `SettingsCategoryContribution`, routed by the extension manager). The
+/// settings panel reads this to build its rail + panels (T-447/T-448) and
+/// rebuilds when the set changes.
+class SettingsRegistry extends ChangeNotifier {
+  final Map<String, SettingsCategory> _byId = <String, SettingsCategory>{};
+
+  /// Registered categories, sorted by (priority, then case-insensitive title).
+  List<SettingsCategory> get categories {
+    final list = _byId.values.toList()
+      ..sort((a, b) {
+        final p = a.priority.compareTo(b.priority);
+        return p != 0 ? p : a.title.toLowerCase().compareTo(b.title.toLowerCase());
+      });
+    return List.unmodifiable(list);
+  }
+
+  SettingsCategory? byId(String id) => _byId[id];
+
+  /// Register a category. Throws on a duplicate id — a collision is a wiring
+  /// bug that should roll the contributing extension's activation back, the
+  /// same way duplicate command/slot ids do.
+  void register(SettingsCategory category) {
+    if (_byId.containsKey(category.id)) {
+      throw StateError('duplicate settings category id: ${category.id}');
+    }
+    _byId[category.id] = category;
+    notifyListeners();
+  }
+
+  void unregister(String id) {
+    if (_byId.remove(id) != null) notifyListeners();
+  }
+}

lib/kernel/src/settings_schema.dart

@@ -0,0 +1,103 @@
+/// Schema model for the settings panel (T-448, epic T-444).
+///
+/// Pure data — no Flutter imports — so any subsystem can declare a category
+/// without depending on the widget layer. The settings-ui renderer turns a
+/// [SettingsCategory] into carded sections of field rows; each field binds to
+/// a `SettingsStore` key and is read/written through the store.
+library;
+
+/// The control a [SettingsField] renders as.
+enum SettingsFieldKind {
+  /// On/off boolean.
+  toggle,
+
+  /// One value chosen from [SettingsField.options].
+  select,
+
+  /// Free-text input.
+  text,
+
+  /// Numeric input (optionally bounded by [SettingsField.min]/[max]).
+  number,
+
+  /// A row that opens an external file/editor (e.g. `.editorconfig`) instead
+  /// of editing a value inline — the action is a command id, keeping the
+  /// schema widget-free.
+  file,
+}
+
+/// One choice in a [SettingsFieldKind.select] field.
+class SettingsOption {
+  const SettingsOption({required this.value, required this.label});
+
+  /// Stored value.
+  final String value;
+
+  /// Human label shown in the picker.
+  final String label;
+}
+
+/// One editable setting. [key] is a `SettingsStore` key — its `app.`/
+/// `project.`/`ext.` prefix determines the scope (and the per-field scope tag,
+/// T-449). The renderer reads the current value with `store.get`, falling back
+/// to [defaultValue] when unset, and writes edits with `store.set`.
+class SettingsField {
+  const SettingsField({
+    required this.key,
+    required this.kind,
+    required this.label,
+    this.help,
+    this.defaultValue,
+    this.options = const [],
+    this.min,
+    this.max,
+    this.fileCommand,
+  });
+
+  final String key;
+  final SettingsFieldKind kind;
+  final String label;
+
+  /// Optional one-line help shown under the label.
+  final String? help;
+
+  /// Value shown / restored when the key is unset (reset-to-default target).
+  final Object? defaultValue;
+
+  /// Choices for [SettingsFieldKind.select].
+  final List<SettingsOption> options;
+
+  /// Optional inclusive bounds for [SettingsFieldKind.number].
+  final num? min;
+  final num? max;
+
+  /// For [SettingsFieldKind.file]: the command id the row's button invokes.
+  final String? fileCommand;
+}
+
+/// A carded group of fields (surface.md "sectioned cards"). [label] is the
+/// small-caps header rendered just above the card.
+class SettingsSection {
+  const SettingsSection({required this.label, required this.fields});
+
+  final String label;
+  final List<SettingsField> fields;
+}
+
+/// One settings category — a rail entry (T-447) plus the sections its panel
+/// shows. Subsystems register these via `SettingsCategoryContribution`; the
+/// renderer draws them.
+class SettingsCategory {
+  const SettingsCategory({required this.id, required this.title, required this.sections, this.iconName, this.priority = 0});
+
+  final String id;
+  final String title;
+
+  /// Phosphor glyph name, resolved via `PhosphorIcons.byName` at render (T-314).
+  final String? iconName;
+
+  /// Rail ordering — lower sorts first; ties broken by [title].
+  final int priority;
+
+  final List<SettingsSection> sections;
+}