tickets: backlog relevance sweep (sub-T-100)

Swept the 19 backlog tickets with ids below T-100 for relevance against
the current codebase + governance.

Cancelled (obsolete):
- T-26 web-tree-sitter — contradicts the desktop-first guardrail
- T-60 workspace trust prompt — premature; third-party ext loading unshipped
- T-40 PRs tab — unscoped, no extension, data path undecided

Annotated (stale text / mixed state, work still valid):
- T-25, T-27 — app/ path prefix stale post-D-56
- T-8 — mixed Tier-6 completion (theme-picker done, settings-ui stub)
- T-55 — split: tmux persistence done, OS tray still a stub
- T-41 — likely superseded by canvas epic (T-317/D-91)
- T-67 — reframe from one-time audit to coverage ratchet
- T-81 — T-79/T-80 done, #21 obsolete, ~7 items remain

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

lib/builtin/keybindings_ui/src/extension.dart

@@ -26,11 +26,13 @@ class KeybindingsUiExtension extends ClideExtension {
   @override
   Future<void> deactivate() async => _keymap = null;
 
-  /// Presets that ship today. VS Code / JetBrains (T-64/T-66) join here
-  /// once their YAMLs land.
+  /// Presets that ship today, each exposed as a `keymap.preset.<name>`
+  /// command that activates it.
   static const _presets = <String, String>{
     'default': 'Keymap: Default',
     'vim': 'Keymap: Vim',
+    'vscode': 'Keymap: VS Code',
+    'jetbrains': 'Keymap: JetBrains',
   };
 
   @override