feat(tui): add a mini help menu when u write ? in the input field

it feels so nice :3 just a lil popup ! doesn't get in the way or take
any focus or anything, and directs users to /help for more info :3

ui-tui/src/components/appLayout.tsx

@@ -22,6 +22,7 @@ import { GoodVibesHeart, StatusRule, StickyPromptTracker, TranscriptScrollbar }
 import { FloatingOverlays, PromptZone } from './appOverlays.js'
 import { Banner, Panel, SessionPanel } from './branding.js'
 import { FpsOverlay } from './fpsOverlay.js'
+import { HelpHint } from './helpHint.js'
 import { MessageLine } from './messageLine.js'
 import { QueuedMessages } from './queuedMessages.js'
 import { LiveTodoPanel, StreamingAssistant } from './streamingAssistant.js'
@@ -242,6 +243,8 @@ const ComposerPane = memo(function ComposerPane({
           pagerPageSize={composer.pagerPageSize}
         />
 
+        {composer.input === '?' && !composer.inputBuf.length && <HelpHint t={ui.theme} />}
+
         {!isBlocked && (
           <>
             {composer.inputBuf.map((line, i) => (