feat(ui): add in-game debug console with tilde toggle and command dispatch (#581)

- debug_console.gd: new ModalLayer Control — tilde key toggles bottom-40% panel,
  command history (up/down), SimBridge dispatch for all DebugCommandKind variants:
  ticks, contaminate, tp, activate, triangle, npc, triangles, pop, status, help
- debug_console.tscn: minimal scene node; UI built programmatically in _ready()
- input_mapper.gd: DEBUG_COMMAND action added to Action enum
- sim_bridge.gd: DEBUG_COMMAND → "DebugCommand" wire mapping
- protocol.gd: v18 debug_response decode (command, text, success fields)
- game_state.gd: debug_response field + apply_snapshot one-shot handling
- main.gd: @onready ref, router registration, _consume_debug_response(), settings signal
- settings_dialog.gd: debug_console_toggled signal + CheckButton toggle row (+36px height),
  reads initial state from user://settings.cfg; CheckButton state loaded from PREFS_PATH
- main.tscn: DebugConsole node on ModalLayer, load_steps 27→28

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/scripts/autoloads/game_state.gd

@@ -81,6 +81,11 @@ var rng_seed: Variant = null
 # One-shot: consumed by main.gd after display, then set back to null.
 var save_result: Variant = null
 
+# v18 fields (#580): debug console response from server.
+# {command: String, text: String, success: bool} or null.
+# One-shot: consumed by main.gd and forwarded to DebugConsole, then set to null.
+var debug_response: Variant = null
+
 # #257: Pending load path — set by main menu "Load Game" selection.
 # main.gd sends LOAD_GAME on startup if non-empty, then clears this field.
 # Format: user://saves/<game-id>/<filename>.sav or "" if no pending load.
@@ -311,6 +316,12 @@ func apply_snapshot(snapshot: Dictionary) -> void:
 	else:
 		save_result = null
 
+	# v18: debug_response (#580) — debug console command result.
+	if snapshot.has("debug_response") and snapshot.debug_response is Dictionary:
+		debug_response = snapshot.debug_response
+	else:
+		debug_response = null
+
 	# v14: player_knowledge (#264, D-041) — partial KG dump for journal panel.
 	# Only update when field is present (null means no change, server sends when KG changes).
 	if snapshot.has("player_knowledge") and snapshot.player_knowledge is Dictionary:

client/scripts/autoloads/input_mapper.gd

@@ -24,6 +24,7 @@ enum Action {
 	TELEPORT_HUB,  # #501: Home key — Gauntlet dev teleport (not production fast-travel)
 	SAVE_GAME,  # #554: F5 quicksave — sends SaveGame to server with save path
 	LOAD_GAME,  # #554: F6 quickload — sends LoadGame to server with save path
+	DEBUG_COMMAND,  # #581: debug console command dispatch — sends DebugCommandKind to server
 }
 
 var input_queue: Array[Dictionary] = []

client/scripts/autoloads/sim_bridge.gd

@@ -416,6 +416,8 @@ static func action_enum_to_wire(action: int) -> String:
 			return "SaveGame"  # #554: F5 quicksave (D-085)
 		InputMapper.Action.LOAD_GAME:
 			return "LoadGame"  # #554: F6 quickload (D-085)
+		InputMapper.Action.DEBUG_COMMAND:
+			return "DebugCommand"  # #581: debug console command dispatch
 		_:
 			push_warning("SimBridge: unknown action enum %s" % action)
 			return ""

client/scripts/main.gd

@@ -22,6 +22,7 @@ extends Node2D
 @onready var bug_report_dialog = $ModalLayer/BugReportDialog  # #495: F12 WRONG button
 @onready var settings_dialog = $ModalLayer/SettingsDialog     # #528: audio settings (ESC/OPEN_MENU)
 @onready var loading_screen = $ModalLayer/LoadingScreen       # #257: blocking overlay during load
+@onready var debug_console = $ModalLayer/DebugConsole         # #581: tilde debug console
 
 var _last_dialogue_npc_id: int = -1  # D-064: NPC entity_id for WalkAway input
 var _last_dialogue_npc_name: String = ""  # #535: NPC name for dialogue_response attribution
@@ -122,6 +123,11 @@ func _ready() -> void:
 	_router.register("conversation_ended", _consume_conversation_ended)
 	_router.register("dialogue_response", _consume_dialogue_response)
 	_router.register("save_result", _consume_save_result)
+	_router.register("debug_response", _consume_debug_response)
+
+	# #581: Wire settings_dialog debug console toggle → debug_console.set_enabled
+	if settings_dialog and debug_console:
+		settings_dialog.debug_console_toggled.connect(debug_console.set_enabled)
 
 
 func _process(delta: float) -> void:
@@ -382,6 +388,8 @@ func _consume_dialogue_response() -> void:
 	if GameState.dialogue_response == null or not dialogue_box:
 		return
 	var dr: Dictionary = GameState.dialogue_response
+	# v0.1: falls back to _last_dialogue_npc_id if wire omits speaker_entity_id.
+	# Edge case: fast re-engagement with a different NPC could misattribute — low probability.
 	var speaker_entity_id: int = dr.get("speaker_entity_id", _last_dialogue_npc_id)
 	var speaker_color_index: int = dr.get("speaker_color_index", -1)
 	var speaker_name: String = dr.get("speaker_name", _last_dialogue_npc_name)
@@ -414,6 +422,14 @@ func _consume_save_result() -> void:
 		monologue_display.show_notification(msg)
 
 
+# #581: Forward debug_response from server to the debug console.
+func _consume_debug_response() -> void:
+	if GameState.debug_response == null or not debug_console:
+		return
+	debug_console.append_response(GameState.debug_response)
+	GameState.debug_response = null
+
+
 # D-061: Handle dialogue option selection → send to server
 func _on_dialogue_option_selected(response_id: String, text: String) -> void:
 	SimBridge.send_input({

client/scripts/protocol/protocol.gd

@@ -244,6 +244,17 @@ static func decode_snapshot(bytes: PackedByteArray) -> Variant:
 			"error": raw_save.get("error"),
 		}
 
+	# v18: debug_response (#580) — debug console command result.
+	# {command: String, text: String, success: bool}
+	var debug_response: Variant = null
+	var raw_debug: Variant = raw.get("debug_response")
+	if raw_debug is Dictionary:
+		debug_response = {
+			"command": str(raw_debug.get("command", "")),
+			"text": str(raw_debug.get("text", "")),
+			"success": bool(raw_debug.get("success", false)),
+		}
+
 	# TODO(server): Send stationary_ticks in ObserverSnapshot (D-071, D-020).
 	# Server already tracks this in ListeningFocus component (server/src/simulation/listening.rs).
 	# When server populates this field, client-side accumulation fallback in game_state.gd
@@ -320,6 +331,7 @@ static func decode_snapshot(bytes: PackedByteArray) -> Variant:
 		"examine_result": examine_result,
 		"player_knowledge": player_knowledge,
 		"save_result": save_result,
+		"debug_response": debug_response,
 		"stationary_ticks": stationary_ticks,
 		"zone_id": zone_id,
 	}