feat(host/windows): PUNKTFUNK_NO_WGC — force single-process DDA everywhere

A single test flag to bring up / validate DDA on its own and as the base for the
secure-desktop work. When set it (1) skips WGC in capture_virtual_output (forces
dxgi::DuplCapturer, same as PUNKTFUNK_CAPTURE=dda) and (2) makes should_use_helper
return false, so even a SYSTEM host bypasses the two-process WGC relay and captures
in-process with one DDA capturer for both the normal AND the secure desktop —
Apollo's model. All the WGC / relay code stays compiled; unset the flag to restore.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/punktfunk-host/src/capture.rs

@@ -258,6 +258,16 @@ pub fn capture_virtual_output(vout: crate::vdisplay::VirtualOutput) -> Result<Bo
     linux::PortalCapturer::from_virtual_output(vout).map(|c| Box::new(c) as Box<dyn Capturer>)
 }
 
+/// `PUNKTFUNK_NO_WGC=1` forces the pure single-process DDA (Desktop Duplication) path everywhere: it
+/// skips WGC in [`capture_virtual_output`] AND bypasses the two-process secure-desktop relay (so even a
+/// SYSTEM host captures in-process via DDA, the way Apollo does — one capturer for the normal AND the
+/// secure desktop). For bringing DDA up to parity / validating it on its own; all the WGC code stays
+/// compiled and comes back the moment the flag is unset.
+#[cfg(target_os = "windows")]
+pub(crate) fn wgc_disabled() -> bool {
+    std::env::var_os("PUNKTFUNK_NO_WGC").is_some()
+}
+
 #[cfg(target_os = "windows")]
 pub fn capture_virtual_output(vout: crate::vdisplay::VirtualOutput) -> Result<Box<dyn Capturer>> {
     let target = vout.win_capture.clone().ok_or_else(|| {
@@ -275,7 +285,7 @@ pub fn capture_virtual_output(vout: crate::vdisplay::VirtualOutput) -> Result<Bo
     let backend = std::env::var("PUNKTFUNK_CAPTURE")
         .unwrap_or_default()
         .to_ascii_lowercase();
-    if backend == "dda" || backend == "dxgi" {
+    if backend == "dda" || backend == "dxgi" || wgc_disabled() {
         return dxgi::DuplCapturer::open(target, pref, keep)
             .map(|c| Box::new(c) as Box<dyn Capturer>);
     }

crates/punktfunk-host/src/m3.rs

@@ -2266,10 +2266,12 @@ fn virtual_stream(
 /// Should this host take the two-process (SYSTEM host + user-session WGC helper) path? Yes when it's
 /// running as SYSTEM — the only account that can capture the secure desktop + drive SendInput on it,
 /// and the account under which in-process WGC won't activate. `PUNKTFUNK_FORCE_HELPER` forces it on
-/// (for testing the relay as a normal user); `PUNKTFUNK_NO_HELPER` forces it off.
+/// (for testing the relay as a normal user); `PUNKTFUNK_NO_HELPER` forces it off. `PUNKTFUNK_NO_WGC`
+/// also forces it off — that mode runs pure single-process DDA (one capturer for the normal AND secure
+/// desktop, Apollo-style), which has no WGC helper to relay.
 #[cfg(target_os = "windows")]
 fn should_use_helper() -> bool {
-    if std::env::var_os("PUNKTFUNK_NO_HELPER").is_some() {
+    if std::env::var_os("PUNKTFUNK_NO_HELPER").is_some() || crate::capture::wgc_disabled() {
         return false;
     }
     std::env::var_os("PUNKTFUNK_FORCE_HELPER").is_some()