test(simulation): sprint 10 — replay loading, content scaling, serialization v9, observer tests

#483: Replay loading in test-client — JSONL file loading, tick-scheduled
PlayerInput sending, 13 unit tests, 3 sample replay files.
#500: Content scaling test — baseline + extra NPC comparative, tick budget
assertion (D-026), determinism check across content packs.
#514: Serialization tests for protocol v9 — blocked_entities roundtrip,
backward compat (v5→v9, v8→v9), regenerated msgpack fixtures.
Observer perception tests for confrontation + walk-away mechanics.

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

server/tests/golden/proof_room_tick_10.json

@@ -1,4 +1,7 @@
 {
+  "blocked_entities": [
+    2
+  ],
   "current_monologue": null,
   "dialogue_response": null,
   "entities": [
@@ -62,7 +65,7 @@
   "player_inventory": [],
   "player_stance": "Sprint",
   "tick": 8,
-  "version": 8,
+  "version": 9,
   "visible_tiles": [
     {
       "tile_kind": "Wall",