keyboard-operable ClideTappable + palette nav (T-100)

Plug widgets into the keymap layer landed in T-117.

ClideTappable:
  - Wrap in `Actions(ActivateIntent → onTap)` outside a `Focus` so
    dispatch from the focused context walks up and hits the action.
  - Add a focus ring via `tokens.globalFocus` (DecoratedBox foreground
    overlay, transparent border when unfocused, no layout shift).
  - Disabled (`onTap == null`) skips focus traversal and shows the
    forbidden cursor.

ClidePalette:
  - Register Actions for the four palette intents
    (selectNext / selectPrev / accept / dismiss).
  - Publish `palette.open` scope flag via `KeymapService.setScopeFlag`
    so when-clauses can scope future bindings to "palette only".
  - Highlight the selected row with `listItemSelectedBackground`;
    scroll it into view on nav.
  - `PaletteController` grows `selectedIndex` + `selectNext` /
    `selectPrevious` / `acceptSelected`; index resets on open /
    filter change.

Intents.dart drops the `ClideIntent` base — `ActivateIntent` and
`DismissIntent` come from Flutter; clide owns the palette and text-
scale and command-bridge subclasses. `parseIntentId('activate')` →
Flutter's class; same for dismiss. Widget code uses the canonical
Flutter Intent types where they fit.

App root grows a PaletteOpenIntent action that calls
`services.palette.open()`, completing the ctrl/cmd+shift+p path
end-to-end.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/kernel/src/keymap/keymap_service.dart

@@ -23,6 +23,7 @@ import 'dart:io';
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart' show AssetBundle, KeyEvent, HardwareKeyboard, rootBundle;
+import 'package:flutter/widgets.dart' show Intent;
 
 import '../settings.dart';
 import 'intents.dart';
@@ -160,7 +161,7 @@ class KeymapService extends ChangeNotifier {
 
   /// Resolve a [KeyEvent] against the active keymap and current scope.
   /// Returns null when nothing matches.
-  ClideIntent? resolveEvent(KeyEvent event, HardwareKeyboard kb) {
+  Intent? resolveEvent(KeyEvent event, HardwareKeyboard kb) {
     final km = _active;
     if (km == null) return null;
     final chord = KeyChord.fromKeyEvent(event, kb);