add toast notification system (T-50)

Non-modal operation-feedback toasts, bottom-right: a ClideToast card per
severity (success/warning/error/info), auto-dismiss (errors linger), queue
with a visible cap, slide+fade in, manual dismiss, live-region a11y.

ToastService is a MessageBus consumer — components raise a toast by publishing
to the 'toast' channel (publishToast helper), so emitters stay decoupled from
the UI. GitController's push/pull are the first emitters. ToastOverlay mounts
in the app-root Stack.

Also adds comprehensive GitController coverage: importing it for the toast
emitter test first pulled the whole file into the coverage denominator, so the
controller is now tested end to end (status/stage/commit/stash/push/pull).

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

lib/widgets/src/clide_toast.dart

@@ -0,0 +1,160 @@
+import 'package:clide/kernel/kernel.dart';
+import 'package:clide/widgets/src/clide_icon.dart';
+import 'package:clide/widgets/src/clide_tappable.dart';
+import 'package:clide/widgets/src/clide_text.dart';
+import 'package:clide/widgets/src/icons/phosphor.dart';
+import 'package:clide/widgets/src/spacing.dart';
+import 'package:clide/widgets/src/typography.dart';
+import 'package:flutter/widgets.dart';
+
+/// Maps a [ToastSeverity] to its status token + leading glyph. Kept here
+/// (render layer) so the [ToastService] stays theme-free.
+({Color color, ClideIconPainter icon}) _styleFor(ToastSeverity s, SurfaceTokens t) {
+  switch (s) {
+    case ToastSeverity.success:
+      return (color: t.statusSuccess, icon: PhosphorIcons.checkCircle);
+    case ToastSeverity.warning:
+      return (color: t.statusWarning, icon: PhosphorIcons.warningCircle);
+    case ToastSeverity.error:
+      return (color: t.statusError, icon: PhosphorIcons.warningCircle);
+    case ToastSeverity.info:
+      return (color: t.statusInfo, icon: PhosphorIcons.circlesFour);
+  }
+}
+
+/// A single toast card (T-50). Severity-colored leading accent + glyph, the
+/// message, and a dismiss affordance. Slides + fades in on mount; clipped to
+/// a bounded width. No Material — a plain themed container (D-7).
+class ClideToast extends StatefulWidget {
+  const ClideToast({super.key, required this.entry, required this.onDismiss});
+
+  final ToastEntry entry;
+  final VoidCallback onDismiss;
+
+  @override
+  State<ClideToast> createState() => _ClideToastState();
+}
+
+class _ClideToastState extends State<ClideToast> {
+  bool _shown = false;
+
+  @override
+  void initState() {
+    super.initState();
+    // Flip after the first frame so the implicit animations run once, then
+    // settle (no perpetual ticker — keeps widget tests deterministic).
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (mounted) setState(() => _shown = true);
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final tokens = ClideTheme.of(context).surface;
+    final style = _styleFor(widget.entry.severity, tokens);
+    return AnimatedSlide(
+      offset: _shown ? Offset.zero : const Offset(0.25, 0),
+      duration: const Duration(milliseconds: 200),
+      curve: Curves.easeOut,
+      child: AnimatedOpacity(
+        opacity: _shown ? 1 : 0,
+        duration: const Duration(milliseconds: 200),
+        child: Semantics(
+          container: true,
+          liveRegion: true,
+          label: widget.entry.message,
+          child: ConstrainedBox(
+            constraints: const BoxConstraints(maxWidth: 360),
+            child: Container(
+              decoration: BoxDecoration(
+                color: tokens.dropdownBackground,
+                border: Border(left: BorderSide(color: style.color, width: 3)),
+                borderRadius: BorderRadius.circular(4),
+                boxShadow: [BoxShadow(color: tokens.shadowAmbient, blurRadius: 8, offset: const Offset(0, 2))],
+              ),
+              padding: const EdgeInsets.fromLTRB(clideInsetText, clideInsetStandard, clideInsetStandard, clideInsetStandard),
+              child: Row(
+                mainAxisSize: MainAxisSize.min,
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: [
+                  ClideIcon(style.icon, size: clideIconStandard, color: style.color),
+                  const SizedBox(width: clideGapStandard),
+                  Flexible(child: ClideText(widget.entry.message, fontSize: clideFontBody, maxLines: 3, overflow: TextOverflow.ellipsis)),
+                  const SizedBox(width: clideGapStandard),
+                  Semantics(
+                    button: true,
+                    label: 'Dismiss notification',
+                    child: ClideTappable(
+                      onTap: widget.onDismiss,
+                      builder: (ctx, hovered, _) => ClideIcon(
+                        PhosphorIcons.xMark,
+                        size: clideIconStandard,
+                        color: hovered ? tokens.globalForeground : tokens.globalTextMuted,
+                      ),
+                    ),
+                  ),
+                ],
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+/// Renders the live [ToastService] queue anchored bottom-right (T-50).
+/// Mounted as a child of the app-root [Stack] (alongside the palette /
+/// quick-open overlays). Occupies only its corner — non-toast space stays
+/// interactive. Newest toast sits at the bottom.
+class ToastOverlay extends StatefulWidget {
+  const ToastOverlay({super.key});
+
+  @override
+  State<ToastOverlay> createState() => _ToastOverlayState();
+}
+
+class _ToastOverlayState extends State<ToastOverlay> {
+  ToastService? _toast;
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    final next = ClideKernel.of(context).toast;
+    if (!identical(_toast, next)) {
+      _toast?.removeListener(_onChanged);
+      _toast = next;
+      _toast!.addListener(_onChanged);
+    }
+  }
+
+  void _onChanged() {
+    if (mounted) setState(() {});
+  }
+
+  @override
+  void dispose() {
+    _toast?.removeListener(_onChanged);
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final entries = _toast?.entries ?? const <ToastEntry>[];
+    if (entries.isEmpty) return const SizedBox.shrink();
+    return Positioned(
+      right: clideGapMajor,
+      bottom: clideGapMajor,
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        crossAxisAlignment: CrossAxisAlignment.end,
+        children: [
+          for (final e in entries) ...[
+            ClideToast(key: ValueKey('toast.${e.id}'), entry: e, onDismiss: () => _toast?.dismiss(e.id)),
+            const SizedBox(height: clideGapStandard),
+          ],
+        ],
+      ),
+    );
+  }
+}

lib/widgets/widgets.dart

@@ -14,6 +14,7 @@ export 'src/clide_filter_box.dart';
 export 'src/clide_markdown.dart';
 export 'src/clide_marquee.dart';
 export 'src/clide_svg_view.dart';
+export 'src/clide_toast.dart';
 export 'src/clide_icon.dart';
 export 'src/clide_icon_rail.dart';
 export 'src/clide_palette.dart';