Phase 1a: focus spoofing + hook observability

Two problems surfaced in testing: (1) no way to tell whether the injected
hook was actually the input source, and (2) the final design needs the tool
window focused for Steam RPT capture, which would pause/silence games that
react to focus loss. Both are addressed here.

- Focus spoofing (hook/focus_spoof): find the game's main window, subclass it
  to rewrite/swallow WM_ACTIVATE/ACTIVATEAPP/NCACTIVATE/KILLFOCUS, and inline-
  hook GetForegroundWindow/GetActiveWindow/GetFocus to always report the game
  as active. The game keeps running and polling while unfocused.
- Status back-channel (protocol v2): the DLL reports attached/focus-spoof
  flags, game pid/hwnd, a heartbeat, and a cumulative XInputGetState counter.
  The host overlay turns the counter into a live poll rate, so "is the hook
  working" is directly observable.
- Synthetic test-input toggle in the host: forwards a known automated pattern
  (stick circle + periodic A) to prove forwarding independent of the physical
  pad.
- hook_selftest extended to assert the status channel; passes.

Documented the windowed/borderless requirement and the new observable test
flow in the README.

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

hook/src/ipc_client.hpp

@@ -3,6 +3,7 @@
 // forwarded pad state the host publishes each frame.
 #pragma once
 
+#include <atomic>
 #include <cstdint>
 
 #include <windows.h>
@@ -54,6 +55,45 @@ public:
 		return read_pads(*block_, out, count);
 	}
 
+	// --- Status back-channel (hook -> host diagnostics) --------------------
+
+	// Record that the game queried a controller slot; the host turns the
+	// cumulative count into a poll rate to prove the hook is live.
+	void note_query(std::uint32_t user_index)
+	{
+		if (block_ != nullptr)
+		{
+			block_->status.xinput_queries.fetch_add(1, std::memory_order_relaxed);
+			block_->status.last_user_index = user_index;
+		}
+	}
+
+	void mark_attached()
+	{
+		if (block_ != nullptr)
+		{
+			block_->status.game_pid = GetCurrentProcessId();
+			block_->status.attached = 1;
+		}
+	}
+
+	void mark_focus_spoof(bool active, std::uint64_t game_hwnd)
+	{
+		if (block_ != nullptr)
+		{
+			block_->status.focus_spoof = active ? 1u : 0u;
+			block_->status.game_hwnd = game_hwnd;
+		}
+	}
+
+	void heartbeat()
+	{
+		if (block_ != nullptr)
+		{
+			block_->status.heartbeat.fetch_add(1, std::memory_order_relaxed);
+		}
+	}
+
 private:
 	SharedMemory shm_;
 	SharedBlock* block_ = nullptr;