feat(desktop): add menu-bar tray companion - #52365

Adds an opt-out OpenCode menu-bar (macOS) / system-tray (Windows, Linux) companion that lists the active session tabs and offers quick actions. It works from the desktop app and from the terminal app.

Menu

Needs you
  [favicon•] Fix login
             dashboard · Context 52% · $0.12
Active sessions
  [ • ]      CSV export                       ← working
             cli · Context 18% · $0.03
  [favicon•] Refactor auth                    ← finished, not yet viewed (blue dot)
             api · No context · $0.00
────────────
New Agent…   ⌘N
Settings     ⌘,
Docs
────────────
Quit         ⌘Q

• Lists open session tabs only, not history. Sessions with questions or permission requests appear under Needs you.
• A working session shows a dot. A blue corner dot means the session finished and has not been viewed. An attention dot means it needs input. The menu-bar icon also gets a dot when any session needs attention.
• Favicons use the desktop's resolved project colours and overrides. Titles and project names are truncated. Tooltips show Local or Worktree, the context percentage, and the cost.
• ⌘⌥O opens the menu from anywhere (Ctrl+Alt+O on Linux, Win+Alt+O on Windows, because Ctrl+Alt is AltGr on many layouts). On Windows, the footer items are plain options without shortcut labels.

Two hosts, one tray

flowchart LR
  subgraph Desktop
    R[Renderer tabs] -- AppSetTrayTabs --> M[Electron main]
  end
  subgraph Terminal
    T[TUI tabs] -- state --> B[CLI bridge<br/>127.0.0.1 + bearer token]
    B <-- poll /state, POST /command --> C[Electron tray-only companion]
  end
  M --> S[(OpenCode service)]
  C --> S
  M --> Tray
  C --> Tray

• Desktop: the renderer publishes open tabs and avatars. The main process loads session status, context, and cost from the service (native/tray-sessions.ts). Tray actions go to the window that owns the session.
• Terminal: opencode (bun run dev locally) starts an authenticated loopback bridge (cli/services/terminal-tray.ts) and launches a tray-only Electron entrypoint (desktop/src/main/terminal-tray.ts). New Agent, Settings, and selecting a session run in the TUI. On macOS, the terminal app is also brought to the front. Quitting the companion leaves the TUI running, and the companion exits when the last terminal client exits.
• The bridge contract is in @opencode/schema/terminal-tray:

Command = { type: "session"; sessionID } | { type: "new" | "settings" | "focus" }
State   = { enabled; focused; sessions: string[]; current? }

Opt-out

• Desktop: Settings → General → Menu bar / system tray.
• Terminal: Settings → Terminal → Menu bar / system tray, "tray": { "enabled": false } in cli.json, or OPENCODE_TRAY=0.
• The companion is not launched over SSH, on headless Linux, or for non-interactive commands.

Screenshots