feat(v1-removal): Phase 3.7f — migrate darkMode to strict tile:darkMode:* handlers
Move darkMode:get / darkMode:set from legacy ipc.ts handlers to strict
tile:darkMode:* handlers in tile-ipc.ts. Behavior preserved exactly
(same broadcast on change, same restartRequired tier2 logic).
- ipc.ts: export setDarkModeSetting, drop legacy darkMode:* handlers
(registerDarkModeSettingHandlers() now a no-op kept for callsite)
- tile-ipc.ts: add tile:darkMode:get/set behind trustedBuiltin grant,
import getDarkModeSetting/setDarkModeSetting/applyDarkModeSetting
from ipc.js
- tile-preload.cts: api.darkMode.{get,set} now invoke strict channels
with token
First of 5 namespace migrations in Phase 3.7f. Build green, unit tests
588/588.