fix(security): land the 2026-07 audit fixes — SSRF guards, roster lane, SYSTEM path hygiene

The low/medium findings from the July host+Windows security review, as
implemented in the audit session's working tree:

- Webhooks and library-art fetches refuse loopback/link-local/metadata
  targets and no longer follow redirects (SSRF pivots from the privileged
  host process).
- The paired-client rosters (/clients, /native/clients) move off the
  streaming-client auth lane — one paired device could enumerate every other
  device's name + fingerprint; only the bearer/loopback console keeps them.
- Device-name sanitizing extends to bidi/format control characters
  (spoofable rendering) via the shared native_pairing::is_spoofy_char;
  stream-marker quoting uses the same set.
- The SYSTEM service resolves powershell by its full System32 path —
  CreateProcess checks the launching EXE's own directory first, so a planted
  powershell.exe beside the host binary would have run as SYSTEM.
- The pf-vdisplay driver's opt-in file log moves from world-writable
  C:\Users\Public to WUDFHost's own temp dir.
- GameStream pairing sessions are single-use (removed whatever the outcome).
- Uninstall also removes the pf_mouse driver-store entry (rider from the
  virtual-HID-mouse work).
- openapi.json regenerated (hardened-config-dir doc wording).

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

crates/punktfunk-host/src/mgmt/session.rs

@@ -21,8 +21,8 @@ use std::sync::atomic::Ordering;
 pub(crate) async fn stop_session(State(st): State<Arc<MgmtState>>) -> StatusCode {
     let was_streaming = st.app.streaming.swap(false, Ordering::SeqCst);
     st.app.audio_streaming.store(false, Ordering::SeqCst);
-    *st.app.launch.lock().unwrap() = None;
-    *st.app.stream.lock().unwrap() = None;
+    *st.app.launch.lock().unwrap_or_else(|e| e.into_inner()) = None;
+    *st.app.stream.lock().unwrap_or_else(|e| e.into_inner()) = None;
     // Native plane: the GameStream flags above don't reach it (it runs its own loops off the shared
     // session registry), so signal every live native session to tear down too.
     let native = crate::session_status::count();