feat(sleep-guard): keep the host device awake while IDBots is working

[WuFenG-Hub]

What

Keep the host device awake while IDBots is actively working, so OS sleep never
interrupts running harness work (bot/cowork sessions, scheduled tasks, nightly
dreams). The main process engages Electron's powerSaveBlocker
(prevent-app-suspension) only while at least one work source is active,
and releases it as soon as everything is idle — the OS sleep policy is
untouched outside actual work.

Changes

• src/main/sleepGuard.ts (new) — pure, dependency-injected guard: policy
  (evaluateSleepGuardWork) + idempotent stateful SleepGuard class. No direct
  electron import, fully unit-testable.
• src/main/main.ts — wiring: singleton getSleepGuard(), recomputeSleepGuard()
  over the live work sources (cowork sessions via getActiveSessionIds(),
  scheduled tasks via new Scheduler.getActiveTaskIds(), dreams via
  getDreamingBotIds()), instant triggers on cowork session start/stop and
  runner complete/error, a 20s periodic safety refresh (self-heal), IPC
  powerGuard:status handle + powerGuard:changed broadcast, and release on
  app cleanup.
• src/main/preload.ts + src/renderer/types/electron.d.ts — powerGuard
  API surface for the harness frontend.
• src/renderer/components/SleepGuardBadge.tsx (new) + Sidebar.tsx — amber
  "防休眠中" badge shown while the guard is engaged, hidden when idle, tooltip
  lists the active sources.
• tests/sleepGuard.test.mjs (new) — 8 unit tests, all pass (fake blocker,
  pure DI, no Electron stub needed).
• scripts/sleep-guard-real-host-check.cjs (new) — real-Electron closed-loop
  check driving the compiled module with the real powerSaveBlocker.

Also fixes a pre-existing lint blocker on main: a stale unused
eslint-disable-next-line react-hooks/exhaustive-deps in
MetaBotEditTabs.tsx that failed npm run lint (0-warnings gate).

Verification (all actually run, not code-assertion only)

• npm run lint — 0 errors, 0 warnings
• npm run compile:electron + npm run build — pass
• node --test tests/sleepGuard.test.mjs — 8/8 pass
• Real-host closed loop (node_modules/.bin/electron scripts/sleep-guard-real-host-check.cjs on macOS):
  • 7/7 checks pass, both directions (idle → engage → idle → re-engage → dispose)
  • While engaged, pmset -g assertions shows the OS-level
    PreventUserIdleSystemSleep assertion — system-level evidence, not an
    in-process self-report
  • After release, the assertion is gone

Notes / honest scope

• Work sources implemented: cowork, scheduledTask, dream. A dedicated
  groupTask source (orchestration daemon) has no ready API on main
  (only a raw DB query in cognitiveOrchestrator); orchestration turns mostly
  run inside cowork sessions, which are already covered. An agentGame source
  is not applicable: that module does not exist on the main baseline. The
  20s refresh self-heals anything event-driven updates miss.
• Full app-level UI walk (launching the app and watching the badge during a
  live session) was not performed in this pass; the closed-loop script drives
  the same code path against the real runtime, and the badge is a thin
  renderer subscription to the verified IPC surface.