fix(gemini): sync TUI↔chat and restore session titles

[bbsngg]

Summary

Fixes two user-reported Gemini session bugs and adds a shell-side advisory banner for a Gemini CLI limitation.

Bug #1 — Gemini sessions always showed "Untitled Session" in the sidebar, even after the user sent their first message. Three-pronged fix:

• server/gemini-cli.js: persistGeminiSessionMetadata now writes null instead of the hardcoded placeholder, so upsertSessionFromSource's incoming || existing pattern stops clobbering real titles.
• server/projects.js (buildGeminiSessionsIndex): treat the legacy "Untitled Session" placeholder as empty so the existing firstMessageText fallback can run for rows seeded by older builds.
• Same two-line fix applied to server/nano-claude-code.js for its "Nano Claude Code Session" placeholder.

Bug #2 — Shell↔chat desync on the same session. Root causes turned out to span three layers:

1. gemini --resume accepts "latest" or a numeric index from --list-sessions, not the UUID. server/index.js now resolves UUID → index via execFile('gemini', ['--list-sessions']) before spawning the shell.
2. useProjectsState.ts had a changedFileParts.length >= 2 gate that excluded Gemini's single-segment path ({uuid}.jsonl), blocking chat refetch on file changes. Relaxed to use the basename directly.
3. Gemini TUI writes live conversation state to ~/.gemini/tmp/{projectHash}/chats/session-*.json on every turn but only flushes ~/.gemini/sessions/{uuid}.jsonl periodically. The chat page was only reading the committed jsonl, so TUI activity was invisible for minutes. Now:
   • New helpers in server/projects.js (readGeminiTmpChatSessionId, findGeminiTmpChatFile, convertGeminiTmpChatsToMessages) ingest the tmp/chats blob and map its {type: "user"|"gemini", content, toolCalls} shape into the downstream message format (including tool_use/tool_result entries).
   • getSessionMessages prefers tmp/chats when its mtime ≥ the jsonl's.
   • A new gemini-tmp chokidar watcher on ~/.gemini/tmp resolves change events back to the session UUID and synthesizes a {uuid}.jsonl broadcast so the frontend's existing refetch gate fires without any client-side changes. The identical-snapshot dedup shortcut is bypassed for these events since tmp/chats churn doesn't change the project index.

Advisory banner. The reverse direction (chat → TUI) is inherently one-way: the running Gemini TUI keeps conversation state in memory and never re-reads its session file. src/components/Shell.jsx now writes a yellow \x1b[33m banner when resuming a Gemini session: "Gemini TUI won't see messages sent from the chat page until you exit and re-resume this session".

Test plan

• Start a fresh Gemini session via chat; send a first message. Verify the sidebar title is derived from the message, not "Untitled Session". Confirm sqlite3 ~/.dr-claw/auth.db "SELECT id, display_name FROM session_metadata WHERE provider='gemini';" shows NULL for new rows.
• Open a Gemini session's shell tab; verify the yellow banner appears and that gemini --resume {index} actually attaches to the same session (no new session created).
• Type a new turn in the TUI; within ~1s the chat page should show the new user+assistant messages, including any tool calls Gemini made.
• Type a new turn in chat; exit the TUI (Ctrl-C) and re-resume from the shell — the chat-sent messages should now appear in the TUI.
• Sessions with no tmp/chats file (older sessions, restored from jsonl only) still render correctly from the committed jsonl.
• Nano Claude Code sessions: verify new sessions no longer show "Nano Claude Code Session" as the title.

🤖 Generated with Claude Code