feat(gamepad): multi-controller support on the native plane

Host was already built for 16 pads; the blocker was every client
hard-coding pad 0. This lands the host-side + reference-client contract:

- input.rs: new wire kinds GamepadArrival=14 (declares a pad's type:
  code=GamepadPref byte, flags=pad) and GamepadRemove=13 (flags=seq<<24|pad,
  shares the snapshot seq space via encode/decode_gamepad_remove).
- pf-client-core/gamepad.rs: reworked from a single `open` pad to a
  slots: Vec<Slot> model — every forwarded controller gets a stable
  lowest-free wire index held for its lifetime, per-slot held/axis/touch/
  rumble state, GamepadArrival on open + GamepadRemove on close, and
  feedback routed back per wire index. Automatic forwards all real pads;
  a pin forces single-player.
- punktfunk1.rs: replaced the single-session PadBackend enum with a Pads
  router — per-pad kinds[]/owner[] arrays, lazily-created per-kind managers,
  pure route_decision keeping a live device in its manager across a kind
  change (no ghost/dup). Input thread seq-gates GamepadRemove (clears the
  pad_mask bit, resets rumble) and applies GamepadArrival kinds.
- inject linux/windows backends: add the two new no-op InputKind arms.

Native/session + default-Windows clients (both spawn punktfunk-session)
inherit this. 57 core + 33 client-core + 272 host tests green; clippy clean.

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

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

@@ -425,7 +425,11 @@ impl InputInjector for KwinFakeInjector {
                 self.fake.touch_frame();
             }
             // Gamepads are injected through uinput, not the compositor.
-            InputKind::GamepadState | InputKind::GamepadButton | InputKind::GamepadAxis => {}
+            InputKind::GamepadState
+            | InputKind::GamepadButton
+            | InputKind::GamepadAxis
+            | InputKind::GamepadRemove
+            | InputKind::GamepadArrival => {}
         }
         // Surface protocol errors / disconnects, then push the batch to the compositor.
         self.queue

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

@@ -404,6 +404,8 @@ fn kind_bit(kind: InputKind) -> u32 {
         InputKind::GamepadButton => 10,
         InputKind::GamepadAxis => 11,
         InputKind::GamepadState => 12,
+        InputKind::GamepadRemove => 13,
+        InputKind::GamepadArrival => 14,
     };
     1 << i
 }
@@ -546,7 +548,11 @@ impl EiState {
             InputKind::TouchDown | InputKind::TouchMove | InputKind::TouchUp => {
                 DeviceCapability::Touch
             }
-            InputKind::GamepadState | InputKind::GamepadButton | InputKind::GamepadAxis => return, // uinput path (later)
+            InputKind::GamepadState
+            | InputKind::GamepadButton
+            | InputKind::GamepadAxis
+            | InputKind::GamepadRemove
+            | InputKind::GamepadArrival => return, // uinput path (later)
         };
         self.injected += 1;
         let n = self.injected;
@@ -693,9 +699,11 @@ impl EiState {
                 Some(t) => t.up(ev.code),
                 None => emitted = false,
             },
-            InputKind::GamepadState | InputKind::GamepadButton | InputKind::GamepadAxis => {
-                emitted = false
-            }
+            InputKind::GamepadState
+            | InputKind::GamepadButton
+            | InputKind::GamepadAxis
+            | InputKind::GamepadRemove
+            | InputKind::GamepadArrival => emitted = false,
         }
 
         if emitted {

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

@@ -254,7 +254,11 @@ impl InputInjector for WlrootsInjector {
                     tracing::debug!(vk = event.code, "unmapped VK keycode — dropped");
                 }
             }
-            InputKind::GamepadState | InputKind::GamepadButton | InputKind::GamepadAxis => {} // not yet injected
+            InputKind::GamepadState
+            | InputKind::GamepadButton
+            | InputKind::GamepadAxis
+            | InputKind::GamepadRemove
+            | InputKind::GamepadArrival => {} // 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

@@ -301,6 +301,8 @@ impl InputInjector for SendInputInjector {
             InputKind::GamepadButton
             | InputKind::GamepadAxis
             | InputKind::GamepadState
+            | InputKind::GamepadRemove
+            | InputKind::GamepadArrival
             | InputKind::TouchDown
             | InputKind::TouchMove
             | InputKind::TouchUp => Ok(()),