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>

host/src/injection_panel.hpp

@@ -21,15 +21,14 @@ public:
 
 	void draw();
 
-	// Forward the latest pad snapshot to the injected hook (if connected).
-	void publish(const std::array<PadInfo, kMaxPads>& pads)
-	{
-		server_.publish(pads);
-	}
+	// Forward the latest pad snapshot to the injected hook (if connected). When
+	// test-input mode is on, a synthetic pattern is sent instead of `pads`.
+	void publish(const std::array<PadInfo, kMaxPads>& pads);
 
 private:
 	void refresh_processes();
 	void inject_selected();
+	void draw_hook_status();
 
 	std::vector<ProcessEntry> processes_;
 	char filter_[128] = {};
@@ -39,6 +38,13 @@ private:
 	IpcServer server_;
 	std::string status_;
 	ImVec4 status_color_;
+
+	bool test_input_ = false;
+
+	// Sampled to turn the hook's cumulative query counter into a poll rate.
+	unsigned long long last_query_count_ = 0;
+	double last_sample_time_ = 0.0;
+	double query_rate_ = 0.0;
 };
 
 } // namespace coop