make the clide command surface self-describing

Parity guarantees a verb exists for every UI action, but a verb is
unreachable if nothing advertises it. Add `clide capabilities` — it
reflects the live dispatcher registry to JSON (subsystem, verb, arg
schema) so the surface is discoverable and can't drift from what
dispatches. A thin /clide skill points Claude at it rather than
hard-coding a verb list, so new panels become reachable the moment
they register.

Co-Authored-By: Claude <noreply@anthropic.com>

CHANGELOG.md

@@ -18,6 +18,9 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 
 ### Added
 
+- `clide capabilities` lists the live command surface as JSON (every verb with
+  its subsystem + argument schema), reflected from the dispatcher so it never
+  drifts. A new `/clide` skill points Claude at it for discovery. (T-248)
 - Toast notifications for operation feedback: non-modal cards slide in
   bottom-right, auto-dismiss (errors linger), stack, and are manually
   dismissable, with success/warning/error/info severities. Components raise