Alerts: wire room_too_large, no_stockpile_accepts, bill_blocked

Three alert signals had no UI subscribers — gameplay failures vanished
silently. Now all three feed AlertsLog via translator handlers that
forward to the generic alert_added sink.

- EventBus: new no_stockpile_accepts(item_type, tile) and
  bill_blocked(recipe_label, reason, focus_tile) signals.
- HaulingProvider: per-item-type 30s cooldown; emits when find_best_for
  scan finishes with viable items but no destinations.
- CraftingProvider: per-(workbench, reason) 60s cooldown; emits at the
  skill_too_low and missing_ingredient continue sites. no_workbench
  reason declared for future use but not emitted (the iteration shape
  has no natural site for it).
- AlertsLog: connect + disconnect for all three signals using the same
  has_signal-guarded pattern; translator handlers convert to localized
  alert_added(severity, text, focus_tile).
- AlertsLog catch-up: room_too_large emits during World init, before
  this CanvasLayer mounts. _catch_up_room_too_large() in _ready scans
  World.rooms for rooms > ROOM_AUTOROOF_CAP and replays them, so the
  pre-built cabin's 24-tile-too-large warning lands in the log on every
  boot. Hauling/bill signals fire at runtime so they need no catch-up.

Verified runtime: cabin warning shows up in AlertsLog with severity
'warn' and focus_tile (45, 24) — the cabin top-left.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

autoload/event_bus.gd

@@ -59,3 +59,7 @@ signal pawn_priority_changed(pawn, category: StringName, level: int) ## Emitted
 signal alert_added(severity: StringName, text: String, focus_tile: Vector2i) ## Emitted by gameplay subsystems to surface a player notice. severity = info | warn | danger.
 signal request_wolf_spawn(count: int)              ## Phase 15 EventCatalog → WolfSpawner. Decouples threat-event effects from spawner.
 signal day_ended(summary: Dictionary)              ## Emitted by Clock at dusk→night boundary; carries the end-of-day recap dict.
+
+# Phase 18 — Alert wiring (dangling signals surfaced to AlertsLog).
+signal no_stockpile_accepts(item_type: StringName, tile: Vector2i) ## Emitted by HaulingProvider when an item needs haul but no stockpile accepts it (rate-limited per item_type).
+signal bill_blocked(recipe_label: String, reason: StringName, focus_tile: Vector2i) ## Emitted by CraftingProvider when a bill cannot proceed. reason: missing_ingredient | skill_too_low | no_workbench.