feat: content-blind push notifications — daemon backbone (P2 push, slice 1) - #249

What

Push notifications — the daemon backbone (P2 push, slice 1 of 3). When a session blocks on a tool approval, the daemon now sends a content-blind wake-up to the session owner's registered devices off-LAN, behind a swappable PushTransport seam. Expo Push is the v1 transport; a self-hosted content-blind relay swaps in behind the same interface later.

This is the headless, device-free backbone. codeoid-mobile consumes it after the next codeoid release (slice 2); the self-hosted relay + iOS NSE + background Approve/Deny are slice 3.

Design

• Content-blind by construction. The emit point (SessionManager.#statusObserver) only ever has (sessionId, status) in hand, and the payload carries only { sessionId, kind } + generic copy — never a tool name, args, or description. Even through a third-party transport (Expo), no session content leaves the daemon; the app resolves human-readable context over its authenticated socket on tap.
• Swappable transport. PushTransport (src/daemon/push) is the seam: ExpoPushTransport (v1) → a self-hosted relay (.p8 APNs + FCM + NSE poll-back) later, with no redesign. config.push.transport: "expo" | "none" (default none).
• Owner-scoped routing. push_registrations keys on the ZeroID identity (owner_sub == sessions.created_by), tenant-scoped by account/project — only the session's creator is alerted, never across tenants.
• Off the hot path. Fire-and-forget at the single daemon-wide status chokepoint that fires regardless of client attachment; a best-effort transport that never throws, so a push hiccup can't touch the status path.

Surface

• Protocol: push.register / push.unregister + a PUSH capability (advertised on auth.ok only when a transport is configured, so clients feature-detect).
• Daemon: push_registrations store + owner-scoped CRUD; PushService; the emit; self-scoped handlers (no bespoke scope, mirroring session.ui_response).
• Config: a push block + CODEOID_PUSH_TRANSPORT / CODEOID_EXPO_ACCESS_TOKEN env overrides.

Tests

bun test: store owner/tenant isolation + refresh + owner-scoped delete; Expo content-blindness + batching + auth header + error-swallow; the transport factory; PushService routing; register/unregister over the wire; and an end-to-end emit test that drives a real session to waiting_approval and asserts the outbound Expo payload is content-blind. Lint + typecheck clean; a regression net over protocol / core / config / session-manager is green.

Follow-ups

• Slice 2 (codeoid-mobile, after a release): expo-notifications + register-on-connect + tap→approval + EAS dev build. First push lands on a phone here.
• Slice 3: self-hosted content-blind relay + iOS Notification Service Extension + daemon reverse channel for background Approve/Deny.

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