fix(client): address PR #78 review comments

- Widen world_seed entropy from u32 to full u64 by combining two randi()
  calls (Hoshe warning #1)
- Persist world_seed to save directory and restore on resume_game() so
  loaded sessions maintain D-010 deterministic replay (Tyre warning #2)
- Constrain EntanglementConfig intrigue range based on flat value so
  mundane_ratio stays within D-029 spec [45,55]% (both reviewers)
- Remove dead VIS_PERIPHERAL constant and _grow_bounds() method
- Update test_client_p1 peripheral test for forward-only simplification
- Fix misleading exp_fade shader comment (filter_nearest = hard step)

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

client/scripts/autoloads/session_manager.gd

@@ -33,16 +33,23 @@ func new_game() -> String:
 	GameState.current_game_id = game_id
 
 	# #175: Generate world_seed for deterministic simulation (D-010, D-029).
-	# Uses randi() (u32) for a seed that maps cleanly to Rust u64 via MessagePack.
-	# 4 billion seeds is sufficient entropy for EntanglementConfig variation (D-029).
-	GameState.world_seed = rng.randi()
+	# Combines two randi() calls (u32 each) into full u64 entropy range.
+	# Without this, upper 32 bits are always zero — halving the seed space.
+	GameState.world_seed = (rng.randi() << 32) | rng.randi()
+
+	# Persist world_seed to save directory so resume_game() can restore it.
+	# Without this, loaded sessions would send seed=0, breaking D-010 determinism.
+	_write_seed_file(save_path, GameState.world_seed)
 
 	return game_id
 
 
 ## Resume an existing game session by setting the active game-id.
+## Restores world_seed from the save directory for D-010 deterministic replay.
 func resume_game(game_id: String) -> void:
 	GameState.current_game_id = game_id
+	var save_path := SAVES_DIR + game_id + "/"
+	GameState.world_seed = _read_seed_file(save_path)
 
 
 ## List all game directories under user://saves/ sorted by last-modified (most recent first).
@@ -117,6 +124,24 @@ func _cleanup_quit_dialog() -> void:
 	_quit_dialog = null
 
 
+## Write world_seed to a file in the save directory for session persistence.
+func _write_seed_file(save_path: String, seed: int) -> void:
+	var file := FileAccess.open(save_path + "world_seed", FileAccess.WRITE)
+	if file == null:
+		push_error("SessionManager: failed to write seed file: %s" % error_string(FileAccess.get_open_error()))
+		return
+	file.store_64(seed)
+
+
+## Read world_seed from save directory. Returns 0 if file missing (legacy saves).
+func _read_seed_file(save_path: String) -> int:
+	var file := FileAccess.open(save_path + "world_seed", FileAccess.READ)
+	if file == null:
+		push_warning("SessionManager: no seed file in %s — using seed=0 (legacy save)" % save_path)
+		return 0
+	return file.get_64()
+
+
 func _find_newest_save(dir_path: String) -> String:
 	var dir := DirAccess.open(dir_path)
 	if dir == null: