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>

tests/replays/gauntlet_hub_teleport.jsonl

@@ -0,0 +1,5 @@
+[{"tick":0,"action":"MoveNorth"}]
+[{"tick":1,"action":"MoveNorth"}]
+[{"tick":2,"action":"MoveEast"}]
+[{"tick":3,"action":"TeleportToHub"}]
+[{"tick":4,"action":"MoveNorth"}]

tests/replays/gauntlet_idle.jsonl

@@ -0,0 +1,5 @@
+[]
+[]
+[]
+[]
+[]

tests/replays/gauntlet_walk_north.jsonl

@@ -0,0 +1,5 @@
+[{"tick":0,"action":"MoveNorth"}]
+[{"tick":1,"action":"MoveNorth"}]
+[{"tick":2,"action":"MoveNorth"}]
+[{"tick":3,"action":"MoveNorth"}]
+[{"tick":4,"action":"MoveNorth"}]