fix(inject/host/windows): fold Steam back grips on the Windows DS/DS4 backends (G7)

The Windows DualSense and DualShock 4 managers passed the raw wire
buttons straight into `DsState::from_gamepad`, so a client's Steam back
grips (BTN_PADDLE1..4) were silently dropped and `PUNKTFUNK_STEAM_REMAP`
was ignored — the Linux DS/DS4 backends already fold them via
`steam_remap::fold_paddles`. Bring the Windows backends to parity: add a
`remap: steam_remap::RemapConfig` field (`::from_env()` in `new()`) to
both managers and fold the paddles before `from_gamepad`, exactly as
`linux/dualsense.rs` / `linux/dualshock4.rs`. Default policy stays Drop
(don't fire buttons the user didn't ask for); set the env to map the
grips onto stick-clicks or shoulders.

`steam_remap` was gated `target_os = "linux"`; widened to
`any(linux, windows)`. It's pure (only punktfunk_core + std::env); its
Linux-only Deck motion rescale is `pub` so it compiles clean on Windows
with no dead-code warning.

Verified: Linux .21 (clippy -D warnings clean, inject tests 32 pass / 0
fail — the gate widening is a no-op there); Windows .173 (clean-recheck
of punktfunk-host, cargo clippy --all-targets -D warnings EXITCODE 0,
steam_remap + both managers compiling on Windows for the first time).
On-glass with a real DualSense/DS4 + PUNKTFUNK_STEAM_REMAP still owed.

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

crates/punktfunk-host/src/inject.rs

@@ -527,7 +527,9 @@ pub mod steam_gadget;
 #[path = "inject/proto/steam_proto.rs"]
 pub mod steam_proto;
 /// Pure fallback-remap policy (Steam-only inputs onto a non-Steam backend) + the Deck motion rescale.
-#[cfg(target_os = "linux")]
+/// Shared by the Linux and Windows DualSense/DS4 backends (the slot-less pads that must fold the
+/// Steam back grips); the Deck motion rescale is Linux-only but harmless to compile on Windows.
+#[cfg(any(target_os = "linux", target_os = "windows"))]
 #[path = "inject/proto/steam_remap.rs"]
 pub mod steam_remap;
 /// Linux: virtual Steam Deck over **USB/IP** (`vhci_hcd`) — the shippable, Secure-Boot-clean,

crates/punktfunk-host/src/inject/windows/dualsense_windows.rs

@@ -389,6 +389,9 @@ pub struct DualSenseWindowsManager {
     /// Create-retry gate: a transient UMDF-channel failure backs off and retries instead of
     /// permanently disabling every pad for the session.
     gate: PadGate,
+    /// Fallback policy for the Steam back grips a client may send (the DualSense has no back-button
+    /// HID slot). `PUNKTFUNK_STEAM_REMAP=paddles=…`; default drop. Parity with `linux/dualsense.rs`.
+    remap: crate::inject::steam_remap::RemapConfig,
 }
 
 impl Default for DualSenseWindowsManager {
@@ -405,6 +408,7 @@ impl DualSenseWindowsManager {
             last_rumble: vec![(0, 0); MAX_PADS],
             last_write: vec![Instant::now(); MAX_PADS],
             gate: PadGate::new(),
+            remap: crate::inject::steam_remap::RemapConfig::from_env(),
         }
     }
 
@@ -433,8 +437,13 @@ impl DualSenseWindowsManager {
                 }
                 self.ensure(idx);
                 let prev = self.state[idx];
+                // Steam back grips have no DualSense slot — fold them onto standard buttons per the
+                // configured policy (default drop) so they aren't silently lost, exactly as
+                // `linux/dualsense.rs` does.
+                let buttons =
+                    crate::inject::steam_remap::fold_paddles(f.buttons, self.remap.paddles);
                 let mut s = DsState::from_gamepad(
-                    f.buttons,
+                    buttons,
                     f.ls_x,
                     f.ls_y,
                     f.rs_x,

crates/punktfunk-host/src/inject/windows/dualshock4_windows.rs

@@ -153,6 +153,9 @@ pub struct DualShock4WindowsManager {
     /// Create-retry gate: a transient UMDF-channel failure backs off and retries instead of
     /// permanently disabling every pad for the session.
     gate: PadGate,
+    /// Fallback policy for the Steam back grips a client may send (the DS4 has no back-button HID
+    /// slot). `PUNKTFUNK_STEAM_REMAP=paddles=…`; default drop. Parity with `linux/dualshock4.rs`.
+    remap: crate::inject::steam_remap::RemapConfig,
 }
 
 impl Default for DualShock4WindowsManager {
@@ -170,6 +173,7 @@ impl DualShock4WindowsManager {
             last_led: vec![None; MAX_PADS],
             last_write: vec![Instant::now(); MAX_PADS],
             gate: PadGate::new(),
+            remap: crate::inject::steam_remap::RemapConfig::from_env(),
         }
     }
 
@@ -199,8 +203,13 @@ impl DualShock4WindowsManager {
                 }
                 self.ensure(idx);
                 let prev = self.state[idx];
+                // Steam back grips have no DS4 slot — fold them onto standard buttons per the
+                // configured policy (default drop) so they aren't silently lost, exactly as
+                // `linux/dualshock4.rs` does.
+                let buttons =
+                    crate::inject::steam_remap::fold_paddles(f.buttons, self.remap.paddles);
                 let mut s = DsState::from_gamepad(
-                    f.buttons,
+                    buttons,
                     f.ls_x,
                     f.ls_y,
                     f.rs_x,