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 ""