perf: eliminate cascading rerenders with granular Zustand selectors

- Delete useDaemonSession hook that selected entire session object
- Move drafts to top-level store (not nested in sessions)
- Refactor all components to use granular useSessionStore selectors
- Fix infinite loop bugs from selector fallbacks (use stable constants)

Before: 15-20 component rerenders per keystroke
After: ~1-2 rerenders per keystroke

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

packages/app/src/contexts/session-context.tsx

@@ -1662,7 +1662,7 @@ export function SessionProvider({ children, serverUrl, serverId }: SessionProvid
     ]
   );
 
-  // Sync imperative methods to Zustand store so useDaemonSession can access them without React Context
+  // Sync imperative methods to Zustand store so components can access them via selectors
   // Memoize the methods object to avoid infinite re-renders (object reference must be stable)
   const setSessionMethods = useSessionStore((state) => state.setSessionMethods);
   const methods = useMemo(() => ({