feat(cli): TUI autocomplete sidebar + fuzzy match + arg hints + input history (P8-017)

- Add CommandAutocomplete component with filtered command list, aliases, arg hints
- Add useInputHistory hook with ring buffer (max 50), up/down navigation, saved input restore
- Wire InputBar with autocomplete state (show on /), Tab/Enter to fill, Escape to dismiss
- Wire up/down arrows: autocomplete navigation when open, history navigation when closed
- Pass allCommands prop from app.tsx commandRegistry to InputBar
- Add 8 pure-logic tests for useInputHistory covering edge cases and caps

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/cli/src/tui/app.tsx

@@ -13,7 +13,7 @@ import { useViewport } from './hooks/use-viewport.js';
 import { useAppMode } from './hooks/use-app-mode.js';
 import { useConversations } from './hooks/use-conversations.js';
 import { useSearch } from './hooks/use-search.js';
-import { executeHelp, executeStatus } from './commands/index.js';
+import { executeHelp, executeStatus, commandRegistry } from './commands/index.js';
 
 export interface TuiAppProps {
   gatewayUrl: string;
@@ -267,6 +267,7 @@ export function TuiApp({
         isStreaming={socket.isStreaming}
         connected={socket.connected}
         placeholder={inputPlaceholder}
+        allCommands={commandRegistry.getAll()}
       />
     </Box>
   );