Phase 16: Save/load full coverage + autosave + UI

Three-agent fan-out reusing the contracts-first pattern: Opus pre-wrote
World.clear_all + 4 EventBus signals (save_started/finished, load_started/
finished) before dispatch. Pattern proven across Phases 12/13/14/15/16.

Entity to_dict/from_dict + class_id tagging (Agent A):
- class_id tag added to all 18 entity to_dict methods for loader routing
- Missing pairs filled in: wolf, grave_slot, graveyard_zone, stockpile_zone,
  crate (from_dict). All defensive with d.get(field, default).
- Workbench round-trips label_text so Carpenter/Smelter/Millstone/Hearth/
  Pyre kinds survive reload
- BeautySystem + DirtinessSystem save_dict/apply_dict for sparse maps
- World.save_tilemap_layers / apply_tilemap_layers covering 5 layers
  (Terrain/Floor/Wall/Designation/Roof; Fog runtime-only skipped)

SaveSystem v2 rewrite (Agent B):
- SAVE_VERSION bumped from 1 to 2
- write_save(slot) pauses Sim, emits save_started, collects every entity
  via _collect_entities iterating all World registries, writes payload to
  user://save_<slot>.json
- apply_save full rewrite: pause sim → emit load_started → World.clear_all
  → apply autoloads (GameState/Clock/Weather/Storyteller) → apply tilemap
  layers → iterate payload.entities and dispatch to per-class factories
  → apply beauty/dirt maps → emit load_finished(slot, ok, real_seconds_away)
- Per-class factory registry: 18 class_ids dispatched to setup+add_child+
  from_dict patterns. CremationPyre detected via workbench.label_text == 'Pyre'
- Public slot API: save_to_slot/load_from_slot/has_save/delete_save/
  peek_save_metadata. Slots locked: &manual + &autosave

Autosave + UI + Resume toast (Agent C):
- autoload/autosave.gd — new Autosave autoload. Periodic every
  AUTOSAVE_INTERVAL_TICKS = 6000 (~5 in-game min at 20 Hz) + NOTIFICATION_
  APPLICATION_PAUSED (mobile) + NOTIFICATION_WM_WINDOW_FOCUS_OUT (desktop).
  Gated by _busy flag tied to EventBus.save_started/save_finished.
- TopBar extended with SaveBtn (💾) + LoadBtn buttons, 48×48 min hit area
- scenes/ui/load_menu.gd — CanvasLayer slot picker. Reads peek_save_metadata
  to show 'Manual save (Date Time)' / 'Autosave (Date Time)' rows.
  Version-mismatch warning dialog before continuing on older saves.
- scenes/ui/resume_toast.gd — top-center toast. On load_finished(ok=true):
  'Welcome back — N minutes/hours away' for 5s + 0.8s fade.
  On ok=false: 'Load failed (corrupt or version mismatch)'.
- Strings catalog: 14 new keys (ui.save / ui.load / ui.welcome_back_* /
  ui.load_failed etc.)
- main.gd mounts LoadMenu + ResumeToast as runtime CanvasLayer children

MCP runtime verified:
- Saved at tick 1137 → [save] wrote slot 'manual': 113 entities at tick 1137
- Advanced sim to tick 4600 at ULTRA speed (different state)
- load_from_slot(&manual) → [save] applied slot 'manual': 113 entities,
  0 errors, tick=1137, away=34s
- post-load: Sim.tick=1137 (restored), pawns alive=3, all furniture +
  workbenches + crops + walls + floors back in place
- Resume toast fires: [resume_toast] showing — ok=true seconds_away=34
- Autosave on focus-loss verified: [autosave] focus-loss → wrote autosave
- Screenshot shows TopBar with Save + Load buttons + post-load Lone Wolf
  storyteller modal from fresh dawn roll

Known acceptable gaps (deferred to Phase 20 tuning):
- Pawn JobRunner mid-INTERACT/mid-BUILD restarts from toil 0 on reload
  (walk toil round-trips; multi-step interact does not). Pawns lose a few
  seconds of work.
- Workbench bill mid-craft fetch state isn't fully serialized.
- Wolf.target_pawn re-resolution from name string is Agent A's documented
  pattern; Agent B's apply_save respects pawn-restoration ordering so the
  resolution works after pawns are back.

Delegation: 3× gdscript-refactor (Sonnet) agents in parallel; integration
+ MCP verify on Opus.

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

autoload/autosave.gd

@@ -0,0 +1,78 @@
+extends Node
+## Autosave trigger — owns periodic + app-pause + focus-loss autosave logic.
+##
+## Does NOT own the write logic (that is SaveSystem.save_to_slot). This node
+## only decides *when* to fire an autosave.  It gates on _busy so we never
+## start a save while another save/load is in-flight.
+##
+## Periodic cadence: every AUTOSAVE_INTERVAL_TICKS sim ticks (~5 in-game minutes
+## at 20 Hz × Fast speed).  The tick counter resets on every save_finished so
+## that a manual save also resets the periodic clock.
+##
+## App-pause (mobile) and focus-loss (desktop) are immediate triggers.
+
+const AUTOSAVE_INTERVAL_TICKS: int = 6000  # 20 Hz × 300 s = 5 in-game minutes
+
+## Set true while a save or load is in progress so we don't re-enter.
+var _busy: bool = false
+## Counts sim ticks since the last autosave (or last save_finished, whichever
+## came last) so we respect the interval even across manual saves.
+var _ticks_since_save: int = 0
+
+
+func _ready() -> void:
+	EventBus.sim_tick.connect(_on_sim_tick)
+	EventBus.save_started.connect(_on_save_started)
+	EventBus.save_finished.connect(_on_save_finished)
+	EventBus.load_started.connect(_on_load_started)
+	EventBus.load_finished.connect(_on_load_finished)
+	Audit.log("autosave", "Autosave ready — interval %d ticks" % AUTOSAVE_INTERVAL_TICKS)
+
+
+func _notification(what: int) -> void:
+	match what:
+		NOTIFICATION_APPLICATION_PAUSED:
+			# Mobile: app sent to background — save immediately.
+			_trigger_autosave("app-pause")
+		NOTIFICATION_WM_WINDOW_FOCUS_OUT:
+			# Desktop: window lost focus — save immediately.
+			_trigger_autosave("focus-loss")
+
+
+# ── signal handlers ───────────────────────────────────────────────────────────
+
+func _on_sim_tick(tick_number: int) -> void:
+	if _busy:
+		return
+	_ticks_since_save += 1
+	if _ticks_since_save >= AUTOSAVE_INTERVAL_TICKS:
+		_trigger_autosave("periodic save at tick %d" % tick_number)
+
+
+func _on_save_started(_slot: StringName) -> void:
+	_busy = true
+
+
+func _on_save_finished(_slot: StringName, _ok: bool) -> void:
+	_busy = false
+	# Reset the periodic counter so any save (manual or auto) restarts the clock.
+	_ticks_since_save = 0
+
+
+func _on_load_started(_slot: StringName) -> void:
+	_busy = true
+
+
+func _on_load_finished(_slot: StringName, _ok: bool, _seconds: int) -> void:
+	_busy = false
+	_ticks_since_save = 0
+
+
+# ── helpers ───────────────────────────────────────────────────────────────────
+
+func _trigger_autosave(reason: String) -> void:
+	if _busy:
+		Audit.log("autosave", "skipped (%s) — save already in progress" % reason)
+		return
+	Audit.log("autosave", reason)
+	SaveSystem.save_to_slot(&"autosave")