feat(inject): shared PadSlots<P> slot table + lifecycle (3.3 layer 1)

The Vec<Option<Pad>> slot table, active_mask unplug sweep, and PadGate-
checked create that all seven backend managers copy-paste, extracted into
one unit-tested inject/pad_slots.rs (cfg any(linux,windows), like
pad_gate). sweep() returns the swept indices as a bitmask and ensure()
returns fresh-create, so managers reset their per-index sibling state
(state / last_rumble / dedup / clocks) without closure gymnastics.
Lifecycle log lines are label/device/hint-parameterized to stay
byte-identical per backend; open() keeps the success line (it knows the
transport detail).

Additive only — no manager converted yet; first unit coverage for the
sweep/create lifecycle (5 tests: freshness, sweep-once semantics, gate
integration, recreate, pump iteration).

Verified on .21: clippy --all-targets -D warnings clean; suite 285
pass / 0 fail (280 prior + 5 new).

Part of G12/3.3 (gamepad-review-cleanup.md §3a.3, commit 2 of the §3a.4
sequence).

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

crates/punktfunk-host/src/inject.rs

@@ -511,6 +511,12 @@ mod gamepad_raii;
 #[cfg(any(target_os = "linux", target_os = "windows"))]
 #[path = "inject/pad_gate.rs"]
 pub mod pad_gate;
+/// Shared virtual-pad slot table + creation lifecycle ([`pad_slots::PadSlots`]) — the
+/// `Vec<Option<Pad>>` table, `active_mask` unplug sweep, and gate-checked create every backend
+/// manager used to copy-paste (G12).
+#[cfg(any(target_os = "linux", target_os = "windows"))]
+#[path = "inject/pad_slots.rs"]
+pub mod pad_slots;
 /// Linux: virtual Steam Deck via UHID — the kernel `hid-steam` driver binds it as a real Deck.
 #[cfg(target_os = "linux")]
 #[path = "inject/linux/steam_controller.rs"]