fix(input): rock-solid held gamepad state — Android device pinning + seq'd snapshots

Two causes behind one field report (a held trigger jittering mid-game,
Android client → Windows host):

Android folded joystick ACTION_MOVEs from EVERY device into one axis
state. A controller's joystick-classified sibling node (DualSense/DS4
motion sensors) or a second/drifting pad reports every pad axis as 0,
so a held trigger flapped value→0→value on each event interleave. The
mapper now qualifies the source DEVICE (its source classes must include
GAMEPAD — a joystick event's own source is always plain JOYSTICK), pins
to one deviceId until that device disconnects, and merges LTRIGGER/BRAKE
(and RTRIGGER/GAS) with max, the same fold as the Controllers probe.

Underneath, gamepad input rode per-transition events over unreliable,
unordered QUIC datagrams — no sequence numbers, sharing the 4 KiB
oldest-first-shed send buffer — so one dropped or reordered event
corrupted held pad state until the NEXT change. Gamepad state now
travels the way rumble already does: idempotent state, refreshed.
InputKind::GamepadState packs the whole pad + a wrapping u8 seq into
the existing 18-byte layout; the host advertises HOST_CAP_GAMEPAD_STATE
(Welcome trailing byte, offset 67) and applies snapshots through a
per-pad stale-seq gate, skipping frame emits for unchanged refreshes;
the client folds embedder events into snapshots inside NativeClient's
input task (send on change + 100 ms refresh of touched pads), so the
SDL clients (Linux/Windows/session), Android, and Apple (C ABI) are all
covered with zero capture-code changes. Either end older ⇒ the legacy
per-transition path runs unchanged.

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

crates/punktfunk-host/src/inject/linux/kwin_fake_input.rs

@@ -425,7 +425,7 @@ impl InputInjector for KwinFakeInjector {
                 self.fake.touch_frame();
             }
             // Gamepads are injected through uinput, not the compositor.
-            InputKind::GamepadButton | InputKind::GamepadAxis => {}
+            InputKind::GamepadState | InputKind::GamepadButton | InputKind::GamepadAxis => {}
         }
         // Surface protocol errors / disconnects, then push the batch to the compositor.
         self.queue

crates/punktfunk-host/src/inject/linux/libei.rs

@@ -403,6 +403,7 @@ fn kind_bit(kind: InputKind) -> u32 {
         InputKind::TouchUp => 9,
         InputKind::GamepadButton => 10,
         InputKind::GamepadAxis => 11,
+        InputKind::GamepadState => 12,
     };
     1 << i
 }
@@ -545,7 +546,7 @@ impl EiState {
             InputKind::TouchDown | InputKind::TouchMove | InputKind::TouchUp => {
                 DeviceCapability::Touch
             }
-            InputKind::GamepadButton | InputKind::GamepadAxis => return, // uinput path (later)
+            InputKind::GamepadState | InputKind::GamepadButton | InputKind::GamepadAxis => return, // uinput path (later)
         };
         self.injected += 1;
         let n = self.injected;
@@ -692,7 +693,9 @@ impl EiState {
                 Some(t) => t.up(ev.code),
                 None => emitted = false,
             },
-            InputKind::GamepadButton | InputKind::GamepadAxis => emitted = false,
+            InputKind::GamepadState | InputKind::GamepadButton | InputKind::GamepadAxis => {
+                emitted = false
+            }
         }
 
         if emitted {

crates/punktfunk-host/src/inject/linux/wlr.rs

@@ -254,7 +254,7 @@ impl InputInjector for WlrootsInjector {
                     tracing::debug!(vk = event.code, "unmapped VK keycode — dropped");
                 }
             }
-            InputKind::GamepadButton | InputKind::GamepadAxis => {} // not yet injected
+            InputKind::GamepadState | InputKind::GamepadButton | InputKind::GamepadAxis => {} // not yet injected
             // wlroots has no virtual-touch protocol wired here; touch is the libei path only.
             InputKind::TouchDown | InputKind::TouchMove | InputKind::TouchUp => {}
         }

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

@@ -297,9 +297,10 @@ impl InputInjector for SendInputInjector {
                 };
                 self.send(&[key(ki)])
             }
-            // Gamepad goes through ViGEm (separate backend). Touch: no SendInput equivalent -> no-op.
+            // Gamepad goes through the XUSB backend. Touch: no SendInput equivalent -> no-op.
             InputKind::GamepadButton
             | InputKind::GamepadAxis
+            | InputKind::GamepadState
             | InputKind::TouchDown
             | InputKind::TouchMove
             | InputKind::TouchUp => Ok(()),