Per-subsystem hook control: install/remove input, focus, audio at runtime

Add a host->hook control channel (protocol v5 -> v6: HookControl in SharedBlock,
per-subsystem "disabled" flags, 0 = install so the zero-filled default is
unchanged). The worker now reconciles each subsystem every tick: install what's
requested-and-missing, remove what's no longer wanted -- so the audio hooks
re-attach the ring and republish format on a reinstall, and XInput/focus clear
their stale status flags on removal.

Injection panel: a checkbox per subsystem (input forwarding / focus spoof /
audio render-hook) toggles it at runtime, showing the requested vs actual
installed state from the registry, plus DLL heartbeat liveness. The hook-status
section now keys off whether a DLL was injected (host-side) rather than the
input-hook "attached" flag, so it stays visible with input unhooked.

Guards for dependent features: the synthetic-input control is disabled when
input forwarding is off, and the Audio panel explains that mirroring uses
loopback (echo) when the render-hook is off.

Verified against Phantom Brave via coop_audio_probe: starting with audio
requested off installs only input+focus (8 hooks, no capture); re-enabling at
runtime installs the audio hooks (13) and capture starts immediately. All four
tests pass.

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

host/src/injection_panel.cpp

@@ -92,9 +92,15 @@ void InjectionPanel::inject_selected()
 		return;
 	}
 
+	// Publish the desired subsystem state before the hook's first reconcile tick.
+	server_.set_subsystem_enabled(HookSubsys_Input, want_input_);
+	server_.set_subsystem_enabled(HookSubsys_Focus, want_focus_);
+	server_.set_subsystem_enabled(HookSubsys_Audio, want_audio_);
+
 	const InjectResult result = inject_dll(selected_pid_, hook_dll_path());
 	if (result.status == InjectStatus::Ok)
 	{
+		injected_ = true;
 		status_ = "Injected into " + narrow(selected_name_) + " (pid " + std::to_string(selected_pid_) + ").";
 		status_color_ = kGreen;
 	}
@@ -200,6 +206,62 @@ void InjectionPanel::draw_hook_list(const HookStatusView& status)
 	}
 }
 
+// True if any hook of `subsystem` is currently installed in the game.
+static bool subsystem_installed(const HookStatusView& status, std::uint32_t subsystem)
+{
+	const std::uint32_t n = status.hook_entry_count < kMaxHookEntries ? status.hook_entry_count : kMaxHookEntries;
+	for (std::uint32_t i = 0; i < n; ++i)
+	{
+		if (status.hook_entries[i].subsystem == subsystem && status.hook_entries[i].installed)
+		{
+			return true;
+		}
+	}
+	return false;
+}
+
+void InjectionPanel::draw_subsystem_controls(const HookStatusView& status)
+{
+	ImGui::SeparatorText("Subsystems (hook / unhook)");
+
+	struct Row
+	{
+		const char* label;
+		std::uint32_t subsystem;
+		bool* want;
+		const char* depends;
+	};
+	const Row rows[] = {
+	    {"Input forwarding (XInput)", HookSubsys_Input, &want_input_, "controller input reaches the game"},
+	    {"Focus spoof", HookSubsys_Focus, &want_focus_, "the game keeps running unfocused"},
+	    {"Audio render-hook", HookSubsys_Audio, &want_audio_, "audio mirror without echo"},
+	};
+
+	for (const Row& r : rows)
+	{
+		ImGui::PushID(r.label);
+		if (ImGui::Checkbox(r.label, r.want))
+		{
+			server_.set_subsystem_enabled(r.subsystem, *r.want);
+		}
+		ImGui::SameLine();
+		const bool on = subsystem_installed(status, r.subsystem);
+		if (*r.want != on)
+		{
+			ImGui::TextColored(kGrey, "(%s...)", *r.want ? "installing" : "removing");
+		}
+		else
+		{
+			ImGui::TextColored(on ? kGreen : kGrey, on ? "installed" : "off");
+		}
+		if (!*r.want)
+		{
+			ImGui::TextDisabled("   off: %s won't work", r.depends);
+		}
+		ImGui::PopID();
+	}
+}
+
 void InjectionPanel::draw_hook_status(bool debug_details)
 {
 	if (!server_.running())
@@ -209,16 +271,37 @@ void InjectionPanel::draw_hook_status(bool debug_details)
 
 	const HookStatusView status = server_.hook_status();
 
-	ImGui::SeparatorText("Hook status");
-	if (!status.attached)
+	// DLL liveness from the heartbeat (advances ~4x/s while the worker runs).
+	const double now = ImGui::GetTime();
+	if (status.heartbeat != last_heartbeat_)
 	{
-		ImGui::TextColored(kGrey, "Waiting for hook to attach in the game...");
+		last_heartbeat_ = status.heartbeat;
+		last_heartbeat_time_ = now;
+		dll_alive_ = true;
+	}
+	else if (now - last_heartbeat_time_ > 1.5)
+	{
+		dll_alive_ = false;
+	}
+
+	ImGui::SeparatorText("Hook status");
+	if (!injected_)
+	{
+		ImGui::TextColored(kGrey, "Not injected.");
 		return;
 	}
 
-	ImGui::TextColored(kGreen, "Attached (game pid %u)", status.game_pid);
-	ImGui::TextColored(status.focus_spoof ? kGreen : kGrey, "Focus spoof: %s",
-	                   status.focus_spoof ? "active" : "inactive");
+	if (dll_alive_)
+	{
+		ImGui::TextColored(kGreen, "Hook DLL loaded in pid %lu (heartbeat %u)", server_.target_pid(),
+		                   status.heartbeat);
+	}
+	else
+	{
+		ImGui::TextColored(kRed, "Hook DLL not responding (no heartbeat).");
+	}
+
+	draw_subsystem_controls(status);
 	ImGui::TextDisabled("Controller poll rates are in the Controllers panel.");
 
 	draw_hook_list(status);
@@ -263,10 +346,11 @@ void InjectionPanel::draw(bool debug_details)
 
 	if (server_.running())
 	{
-		ImGui::TextColored(kGreen, "Forwarding input to pid %lu", server_.target_pid());
-		if (ImGui::Button("Stop forwarding"))
+		ImGui::TextColored(kGreen, "Connected to pid %lu", server_.target_pid());
+		if (ImGui::Button("Disconnect"))
 		{
 			server_.stop();
+			injected_ = false;
 			status_ = "Stopped.";
 			status_color_ = kGrey;
 		}
@@ -315,7 +399,10 @@ void InjectionPanel::draw(bool debug_details)
 		ImGui::TextColored(status_color_, "%s", status_.c_str());
 	}
 
+	// Synthetic input only reaches the game if the XInput hook is installed.
+	ImGui::BeginDisabled(injected_ && !want_input_);
 	ImGui::Checkbox("Forward synthetic test input", &test_input_);
+	ImGui::EndDisabled();
 	if (test_input_)
 	{
 		ImGui::SameLine();