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/kernel/src/log.dart

@@ -0,0 +1,88 @@
+import 'dart:async';
+import 'dart:io';
+
+enum LogLevel { trace, debug, info, warn, error }
+
+class LogRecord {
+  LogRecord({
+    required this.level,
+    required this.source,
+    required this.message,
+    required this.timestamp,
+    this.error,
+    this.stackTrace,
+  });
+
+  final LogLevel level;
+  final String source;
+  final String message;
+  final DateTime timestamp;
+  final Object? error;
+  final StackTrace? stackTrace;
+
+  @override
+  String toString() {
+    final lv = level.name.toUpperCase().padRight(5);
+    final buf =
+        StringBuffer('${timestamp.toIso8601String()} $lv [$source] $message');
+    if (error != null) buf.write(' | error=$error');
+    return buf.toString();
+  }
+}
+
+typedef LogSink = void Function(LogRecord);
+
+class Logger {
+  Logger({this.minLevel = LogLevel.info, List<LogSink>? sinks})
+      : _sinks = List<LogSink>.from(sinks ?? <LogSink>[stderrSink]);
+
+  LogLevel minLevel;
+  final List<LogSink> _sinks;
+  final StreamController<LogRecord> _stream =
+      StreamController<LogRecord>.broadcast();
+
+  Stream<LogRecord> get records => _stream.stream;
+
+  void addSink(LogSink sink) => _sinks.add(sink);
+
+  void trace(String source, String message) =>
+      _emit(LogLevel.trace, source, message);
+  void debug(String source, String message) =>
+      _emit(LogLevel.debug, source, message);
+  void info(String source, String message) =>
+      _emit(LogLevel.info, source, message);
+  void warn(String source, String message, {Object? error}) =>
+      _emit(LogLevel.warn, source, message, error: error);
+  void error(String source, String message,
+          {Object? error, StackTrace? stackTrace}) =>
+      _emit(LogLevel.error, source, message,
+          error: error, stackTrace: stackTrace);
+
+  void _emit(LogLevel level, String source, String message,
+      {Object? error, StackTrace? stackTrace}) {
+    if (level.index < minLevel.index) return;
+    final rec = LogRecord(
+      level: level,
+      source: source,
+      message: message,
+      timestamp: DateTime.now().toUtc(),
+      error: error,
+      stackTrace: stackTrace,
+    );
+    for (final sink in _sinks) {
+      try {
+        sink(rec);
+      } catch (_) {
+        // a broken sink must not kill logging
+      }
+    }
+    if (!_stream.isClosed) _stream.add(rec);
+  }
+
+  Future<void> dispose() => _stream.close();
+}
+
+void stderrSink(LogRecord r) {
+  stderr.writeln(r);
+  if (r.stackTrace != null) stderr.writeln(r.stackTrace);
+}