Fix ⌘B: dispatch/listen event-name mismatch; thinking pill → "Thinking (⇧⇥)"

Root cause (interlude, owner 2026-09-25): keyboard-shortcuts dispatches
registry actions on the lh:kbd-<action> convention, but the sidebar's
listener sat on the pre-convention name "lh:toggle-sidebar" — a name
nothing ever dispatches, so ⌘B silently did nothing while its tooltip
and cheat-sheet row kept claiming the binding. A sweep of every lh:
listener confirmed the sidebar was the lone stray (chat-renamed and
graph-revision are deliberate non-kbd events).

Fix, structural: kbdEventForAction(action) exported from
src/core/keyboard.ts — the ONE spelling — and both sides compose
through it (dispatcher's default branch, sidebar's toggle listener);
keyboard-shortcuts re-exports the helper so the contract pin can assert
no second spelling exists. The mismatch is now impossible by
construction.

Thinking pill: label trimmed to "Thinking" with its real shortcut via
the registry-composition path — "Thinking (⇧⇥)" (cycle-thinking,
rebind-live like every Hint suffix).

Pins (tests/keyboard-toggle-sidebar.test.ts): the full chain — mod+b →
actionForBinding → toggle-sidebar → kbdEventForAction →
lh:kbd-toggle-sidebar; formatBinding("shift+tab") → ⇧⇥; the
dispatcher-imports-the-same-helper contract.

Live-verified on :3001: ⌘B visually toggles on home, /chat/[id], and
/chat/new (sidebar 0↔288px, hamburger slot 0↔36); with the rebind
lh:keymap {"toggle-sidebar":"mod+j"}: ⌘J toggles and ⌘B is inert
(rebind-live); thinking pill renders "Thinking (⇧⇥)"; keymap restored,
sidebar left open.

components/keyboard-shortcuts.tsx

@@ -31,11 +31,17 @@ import {
 	eventBinding,
 	formatBinding,
 	isTypingSurface,
+	kbdEventForAction,
 	KEYBOARD_ACTIONS,
 } from "@/src/core";
 import { isDictationActive } from "@/components/dictation";
 import { useSettingsDialog } from "@/components/settings/settings-dialog.tsx";
 
+// Re-exported for the contract pin (tests/keyboard-toggle-sidebar.test.ts):
+// the dispatcher composes event names through the ONE helper — a second
+// spelling here is how the ⌘B bug happened.
+export { kbdEventForAction };
+
 export function KeyboardShortcuts() {
 	const router = useRouter();
 	const [cheatOpen, setCheatOpen] = useState(false);
@@ -109,7 +115,7 @@ export function KeyboardShortcuts() {
 					handlersRef.current.setCheatOpen(true);
 					break;
 				default:
-					window.dispatchEvent(new CustomEvent(`lh:kbd-${action}`));
+					window.dispatchEvent(new CustomEvent(kbdEventForAction(action)));
 			}
 		};
 		window.addEventListener("keydown", onKeyDown);