feat(companion): auto-switch Windows audio output on controller headset jack

[gunCannoli]

Problem

The DualSense's audio endpoint stays present in Windows whether or not
anything is plugged into the controller's 3.5 mm jack. Windows frequently
promotes it to the default output device when the controller connects, so
system audio goes to the controller's speaker even with no headset attached.

Windows cannot detect the jack state itself -- the USB audio device does not
disconnect when the headset is unplugged -- so it cannot switch back on its
own. Users have to change the default output manually every time.

Change

Companion-app only. The firmware already reports the jack state: the
DualSense input report's PluggedHeadphones bit reaches the companion as
audioStatus.headsetPlugged. No firmware change is required.

When enabled, the companion drives the Windows default render endpoint:

• Headset in the controller's jack -> the controller / bridge endpoint.
• Jack empty -> a fallback output device.

The fallback is chosen in Bridge Settings. When exactly one non-controller
output exists it is used automatically and no dropdown is shown; with two or
more, a dropdown lists them. This also covers the case where Windows promotes
the controller to default while the jack is empty -- the companion routes
back to the fallback.

Details

• Debounce. The firmware bit is an unfiltered pass-through of the input
  report with no debouncing, so a marginal plug can chatter. A changed jack
  state must hold across two consecutive audio-status polls (~1 s) before the
  companion acts.
• Bit 0, not bit 1. headsetAudioRoute (bit 1) reflects
  firmware-internal speaker routing and is false whenever nothing is playing.
  headsetPlugged (bit 0) is the actual jack state.
• Dormant during RDP. Windows redirects audio to a Remote Audio endpoint
  during a remote session; the feature stays inactive rather than fighting
  it.
• Dormant during host-persona transitions and while the existing persona
  default-render restore is in flight.
• Off by default. Enabling requires the toggle and takes effect only when a
  fallback device can be resolved.

Implementation

• companion/native/AudioHelper -- two new verbs:
  --set-default-render --device-name "A;B;C" (set the default render
  endpoint to the first active match; reuses the existing
  IPolicyConfig::SetDefaultEndpoint path) and --list-render-endpoints
  (active render endpoints as JSON, flagging the bridge's own endpoint).
• bridge-service.ts -- syncHeadsetAudioAutoSwitch(), called once per poll
  after syncControllerPowerSavingState().
• Two settings: headsetAudioAutoSwitchEnabled (bool) and
  headsetAudioFallbackDevice (string; empty means auto-resolve).
• Three IPC channels, one settings row in Bridge Settings.

No COMMAND_ID, no PROTOCOL_MINOR bump, no firmware change.

Settings modal size

This adds one row to Bridge Settings. The preferences modal is already the
tightest variant, and on a fresh checkout the Power & Controller column can
get crowded. This is a UI-layout call for the maintainer and is not
changed in this PR. Our suggestion, if a change is wanted, is to let the
preferences modal fill the app window (the two columns then fit without an
internal scrollbar); a smaller height bump would also work.

Testing

npm run typecheck and npx vitest run src pass. Seven new tests cover the
plug/unplug transitions with debounce, the disabled case, auto-resolution of
a single output, the ambiguous multi-output case, the empty-jack correction,
RDP dormancy, and the IPC contract. npm run build:audio-helper builds
clean.

Hardware (Waveshare RP2350B-Plus-W, Windows 11):

1. Controller connects with an empty jack, Windows promotes it to default --
   output is routed back to the fallback device.
2. Headset plugged in -- output switches to the controller within ~1 s.
3. Unplugged -- output returns to the fallback.
4. Feature disabled -- neither switch occurs.
5. Repeated partial insertions -- no flip-flopping.
6. Two-plus non-controller outputs present -- the dropdown lists them, the
   selected fallback persists, and a saved-but-absent device shows
   "(not connected)".