Phase 1a: per-slot poll viz + input-path diagnostics

Surfaced by a game (Life is Strange: Before the Storm) that ignores
controller input when it lacks true OS focus even though it still polls
XInput. To find the focus-gated detection path, instrument the hook.

Protocol v3 status back-channel now reports:
- per-slot XInputGetState and XInputGetCapabilities counters (replacing the
  single aggregate), so the overlay shows exactly which slots the game polls
  and how fast;
- focus-API call counts (GetForegroundWindow/GetActiveWindow/GetFocus) to see
  whether the game consults the APIs we spoof;
- input-path diagnostics: whether the process registered Raw Input for a
  gamepad usage and whether it set RIDEV_INPUTSINK (background delivery), and
  whether a DirectInput dll is loaded.

Host overlay gains a per-slot poll table and an "Input path" section. The DLL
refreshes input diagnostics each worker tick via GetRegisteredRawInputDevices.
hook_selftest updated for per-slot counters; passes.

This is diagnostic-only: once a real run shows which path LiS uses, the
targeted focus fix (e.g. forcing RIDEV_INPUTSINK or DI background coop) follows.

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

tests/hook_selftest.cpp

@@ -79,7 +79,9 @@ int main()
 
 	// Status back-channel: the host relies on these to prove the hook is live.
 	check(block->status.attached == 1, "status reports attached");
-	check(block->status.xinput_queries.load(std::memory_order_relaxed) >= 2, "status counts XInput queries");
+	check(block->status.get_state_calls[0].load(std::memory_order_relaxed) >= 1, "status counts slot 0 GetState");
+	check(block->status.get_state_calls[1].load(std::memory_order_relaxed) >= 1, "status counts slot 1 GetState");
+	check(block->status.get_caps_calls[0].load(std::memory_order_relaxed) >= 1, "status counts slot 0 GetCaps");
 
 	hook::remove_xinput_hooks();