docs: mark quicksave phase complete

docs/SIMULATION_STATE_SCHEMA.md

@@ -87,15 +87,26 @@ ResourceStateRecord v2 adds the definition facts needed while unloaded. Nested
 v1 resource records are migrated explicitly and hydrate their missing
 definition from a matching presentation node when one becomes available.
 
+## Local quicksave boundary
+
+`SaveSlotStore` writes the existing versioned JSON record to
+`user://saves/quicksave.json`. It validates the serialized record before
+replacement, limits file size, restricts slot names, preserves the previous
+file during replacement, and can recover that backup if replacement is
+interrupted. Loading parses and validates the complete record before mutating
+the simulation.
+
+In `main.tscn`, F5 saves and F9 loads this slot. Restoration rebuilds active NPC
+visuals from authoritative state.
+
 ## Deliberately out of scope
 
 This phase does not yet provide:
 
-- save-slot files, metadata, thumbnails, or atomic disk writes;
+- a save-slot menu, metadata, thumbnails, autosaves, or multiple profiles;
 - migrations older than the explicitly supported world schemas v1 and v2;
 - player inventory, relationship, schedule, or social-memory records;
-- a player-facing load flow;
-- save-slot persistence for scene-independent resource state.
+- persistence for the player transform or presentation-only scene state.
 
 Those features should build on this boundary rather than inventing parallel
 serialization paths.