refactor(windows-host): delete the SudoVDA backend — pf-vdisplay is the sole vdisplay (Goal 2)

Goal 2 ("drop every trace of SudoVDA") is done. The SudoVDA driver is no longer
shipped (only pf-vdisplay; the old vdisplay-driver tree was deleted in a2bd0cd),
and F1 (d638a93/e60cda3) already moved the display-utility helpers out of the
backend into neutral modules (win_adapter/win_display), breaking the reach-in.
So the backend is now cleanly removable:

- Deleted crates/punktfunk-host/src/vdisplay/windows/sudovda.rs (350 lines: the
  SudoVdaDisplay VirtualDisplay impl + its VdisplayDriver/probe).
- vdisplay::open()/probe() are now unconditional pf-vdisplay; deleted the
  windows_use_pf_vdisplay() backend selector. open() now ensure!s
  pf_vdisplay::is_available() with a clear "driver not installed" error instead
  of the old silent SudoVDA fallback (no fallback driver exists anymore).
- Scrubbed the dangling references to the deleted symbols (manager/sendinput/dxgi
  comments, the config + host.env PUNKTFUNK_VDISPLAY docs); the var stays as an
  informational forward-seam. Updated the F1 module docs (Goal 2 now done).

All changes are #[cfg(windows)] except the config doc; Linux clippy
-p punktfunk-host -D warnings clean; zero `sudovda::`/`SudoVdaDisplay` code refs
remain (comments only). Windows build is CI-gated.

Scorecard Goal 2 -> DONE; recorded the E1 "do NOT do it" stability decision in
windows-host-rewrite.md §4 (the process-global driver design is sound given
ProcessSharingDisabled; a device-owned variant adds a use-after-free window for
no gain).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/punktfunk-host/src/windows/win_display.rs

@@ -5,8 +5,8 @@
 //! These are display-utility, NOT SudoVDA-specific (a pf-vdisplay monitor's target_id is a real OS target
 //! id, so they operate identically), so they live here rather than in the SudoVDA backend — breaking the
 //! circular reach-in where the capturers + the pf-vdisplay backend reached into `vdisplay::sudovda` for
-//! them, so SudoVDA can eventually be dropped without losing them (audit §9 / Goal 2). The plan's
-//! `windows/display_ccd.rs`. Moved verbatim from `vdisplay::sudovda`.
+//! them, which let the SudoVDA backend be dropped without losing them (audit §9 / Goal 2 — done). The
+//! plan's `windows/display_ccd.rs`. Extracted verbatim from the former SudoVDA backend before its removal.
 
 use std::mem::size_of;