feat(desktop): emit system.wake on window foreground (#1653)

[mabry1985]

What

Completes the third ADR 0074 lifecycle event. The server-side bus contract for system.wake shipped with #1653 (reserved in the seam/config); this wires the desktop origination: on WindowEvent::Focused(true) the Tauri shell POSTs system.wake to the sidecar's existing /api/events/publish, which broadcasts it on the event bus so lifecycle_hooks reactions (resume interrupted work, refresh state, check inbox) fire on wake.

Design

• Debounced to once per 60 s — focus fires on every alt-tab, so a WakeSignal (sidecar port + a throttle Instant, in Tauri managed state) suppresses rapid re-focus. It's seeded to "now" at setup, so the window's own boot focus is suppressed (no redundant system.wake right after app.loaded).
• Fire-and-forget via tauri::async_runtime::spawn; a down/booting sidecar just logs at debug. Never blocks the UI thread; the throttle lock is dropped before the await.
• Reuses the existing reqwest + port-resolution plumbing — no new endpoint.

Scope

Foreground-focus is the v1 signal. True OS sleep/wake (laptop lid, display sleep) has no Tauri primitive — it'd need native NSWorkspace.didWakeNotification / Windows WM_POWERBROADCAST observers, a deliberate later lift.

Verification

• cargo check passes (compiled lib.rs clean in a worktree, after stubbing the bundled sidecar binary that isn't present there — the stub is not committed).
• DRAFT because the actual wake behavior can't be CI-verified — it needs a desktop build + manual test: run the app, blur it >60 s, refocus, and confirm a system.wake broadcast (e.g. a lifecycle_hooks reaction fires, or watch the sidecar /api/events stream). No Python/CI surface changes.

Closes the desktop system_wake follow-up on #1653.

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[mabry1985]

Review (pre-merge): design is clean — debounce, boot-focus suppression, fire-and-forget all correct, and I confirmed the server-side contract it targets exists (system.wake registered in graph/lifecycle/dispatch.py:33, /api/events/publish at operator_api/routes.py:601, payload shape {topic, data} matches and passes the namespacing guard).

One gap to close before it goes ready: maybe_signal_wake POSTs with no Authorization header. /api/events/publish runs behind the default-deny A2AAuthMiddleware (a2a_impl/auth.py), which only enforces bearer when a token is configured. So:

• Default desktop (loopback, no token) → works.
• Desktop with auth.token / A2A_AUTH_TOKEN set (e.g. tailnet-exposed, per the fleet-frontend pattern) → the POST 401s and system.wake silently never fires. It degrades gracefully (debug log) but the feature is dead for exactly those instances.

The existing chat_stream command already shows the fix — it takes the token and adds req.header("Authorization", token) (lib.rs:617-618). maybe_signal_wake runs native-side with no webview, so it'd need to resolve the token itself (env A2A_AUTH_TOKEN, or the resolved config). Worth wiring, and worth adding to the manual test matrix: test once with a token configured too.

Otherwise 👍 — keep as draft until the desktop-build manual test (blur >60s → refocus → confirm one system.wake broadcast).