feat(host,web): experimental PnP monitor-devnode disable for Exclusive sessions

Second experiment against the connected-but-dark-head stutter (field-proven
on the reporter's box: unplugging his standby HDMI TV removes a metronomic
~4 s double-jolt; DDC/CI is a dead end for TVs — measured on the lab LG, VCP
0xD6 gets no I2C ACK). An Exclusive isolate only removes physical monitors
from the CCD topology; their PnP devnodes stay live, so every standby wake
(auto input scan, Instant-On HPD cycling) still triggers the full Windows
reaction: PnP arrival/removal, CCD re-evaluation, DWM invalidation — the
suspected hiccup mechanism (Apollo #368's Device-Manager-refresh signature).

- New `pnp_disable_monitors` display-policy axis (default off): orthogonal
  to presets like game_session/ddc_power_off, surfaced in GET/PUT
  /display/settings + the enforced list, carried through the layout
  transform.
- windows/monitor_devnode.rs: after the isolate takes, disable exactly the
  deactivated monitors' devnodes — CCD target → monitor device path
  (DISPLAYCONFIG_TARGET_DEVICE_NAME) → PnP instance id → CM_Disable_DevNode
  with CM_DISABLE_PERSIST, so a hot-plug RE-ARRIVAL stays disabled (that
  persistence is the whole point). Teardown re-enables BEFORE the CCD
  restore (+300 ms re-arrival settle) so restored paths have their monitors
  back. Precise selection — co-installed third-party virtual displays are
  never touched.
- Crash safety: instance ids journal to <config>/pnp-disabled-monitors.json
  before disabling; serve startup re-enables leftovers from a crashed host.
  Worst case is documented in the console help (Device Manager re-enable).
- Web console: second Experimental-badged toggle (the DDC block refactored
  into a shared ExperimentalToggle), EN/DE strings, preset-switch carry.

Verified: Linux 263 tests + clippy + fmt clean; Windows (RTX box) 220/220 +
clippy clean; web tsc + production build clean; openapi.json regenerated.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/punktfunk-host/src/mgmt.rs

@@ -1054,6 +1054,7 @@ fn display_settings_state() -> DisplaySettingsState {
             // EXPERIMENTAL, Windows-only in effect: acted on at the `exclusive` isolate
             // (`vdisplay/windows/manager.rs`); stored-but-inert elsewhere.
             "ddc_power_off".into(),
+            "pnp_disable_monitors".into(),
         ],
     }
 }
@@ -1263,6 +1264,7 @@ async fn set_display_layout(ApiJson(req): ApiJson<DisplayLayoutRequest>) -> Resp
         req.positions,
         store.game_session(),
         store.ddc_power_off(),
+        store.pnp_disable_monitors(),
     );
     if let Err(e) = store.set(policy) {
         return api_error(
@@ -2948,8 +2950,9 @@ mod tests {
         assert!(enforced.contains(&"mode_conflict"));
         assert!(enforced.contains(&"identity"));
         assert!(enforced.contains(&"layout"));
-        // The experimental DDC/CI panel-off axis is acted on (Windows exclusive-isolate path).
+        // The experimental DDC/CI + PnP-disable axes are acted on (Windows exclusive-isolate path).
         assert!(enforced.contains(&"ddc_power_off"));
+        assert!(enforced.contains(&"pnp_disable_monitors"));
     }
 
     /// The display state/release endpoints are wired + auth-gated. On the test host no backend has