Add L1 tests for Bluetooth onPowerModeChanged power management behavior

[Copilot]

onPowerModeChanged() had no L1 test coverage for its HID-skip logic and autoConnectStatus-conditional disconnect, leaving critical power transition behavior unverified.

Changes

• New BluetoothPowerModeTest fixture — pre-populates the paired device cache with a "HUMAN INTERFACE DEVICE" entry at init time by mocking GetValue to return the device JSON and BTRMGR_GetPairedDevices to return the matching handle (prevents cache scrubbing in updateCacheFromDevice()).

• onPowerModeChanged test matrix (11 cases across both fixtures):

  Transition	Device	autoConnectStatus	Expected
  ON → same	—	—	no-op
  ON/UNKNOWN → STANDBY/LIGHT_SLEEP	non-HID	DISABLED	BTRMGR_StopAudioStreamingOut called
  ON → STANDBY	non-HID	ENABLED / empty cache	no disconnect
  ON → STANDBY	HID	DISABLED	skipped (no disconnect)
  X → ON	non-HID present	any	BTRMGR_SetAdapterPowerStatus(0, 1)
  X → ON	HID only	any	no SetAdapterPowerStatus
  X → DEEP_SLEEP	non-HID	ENABLED	always disconnects
  X → DEEP_SLEEP	HID	any	skipped
  STANDBY → LIGHT_SLEEP	—	—	unhandled, no-op

• Non-HID devices are injected into the cache via the existing setAutoConnect JSON-RPC call (produces an entry with empty deviceType, which does not match "HUMAN INTERFACE DEVICE").

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