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/widgets/src/clide_icon.dart

@@ -0,0 +1,57 @@
+import 'package:clide/kernel/src/theme/controller.dart';
+import 'package:flutter/widgets.dart';
+
+/// Stateless painter producing a single-color icon. Every icon in
+/// [icons/] subclasses this; widgets wrap with [ClideIcon] for size +
+/// color-from-theme.
+abstract class ClideIconPainter {
+  const ClideIconPainter();
+
+  /// Paint the icon into a unit square (0,0 .. 1,1).
+  void paint(Canvas canvas, Color color);
+}
+
+class ClideIcon extends StatelessWidget {
+  const ClideIcon(
+    this.painter, {
+    super.key,
+    this.size = 14,
+    this.color,
+  });
+
+  final ClideIconPainter painter;
+  final double size;
+  final Color? color;
+
+  @override
+  Widget build(BuildContext context) {
+    final resolved = color ?? ClideTheme.of(context).surface.globalForeground;
+    return SizedBox(
+      width: size,
+      height: size,
+      child: CustomPaint(
+        size: Size(size, size),
+        painter: _IconPainterAdapter(painter: painter, color: resolved),
+      ),
+    );
+  }
+}
+
+class _IconPainterAdapter extends CustomPainter {
+  _IconPainterAdapter({required this.painter, required this.color});
+
+  final ClideIconPainter painter;
+  final Color color;
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    canvas.save();
+    canvas.scale(size.width, size.height);
+    painter.paint(canvas, color);
+    canvas.restore();
+  }
+
+  @override
+  bool shouldRepaint(covariant _IconPainterAdapter old) =>
+      old.painter != painter || old.color != color;
+}