feat(playable): 首个 Mac 联网内测版 STB-01 soak 工具与发布状态文档

- 新增 script/playable_soak.sh：先做 soak 配置/资源校验，无 --allow-gameplay
  只校验不启动客户端；N(>=10) 次独立正常退出运行 + 墙钟 soak，失败即停止后续
  运行并记 BLOCKED；写本批次 release-manifest.json 后聚合
- run_client_gate.sh：确认的故障代理对所有 suite 启动（共享场景的退出运行也经代理）；
  soak 超时下限只约束 soak 客户端（validate_soak 增加 soak_client 参数）
- 新增本地 127.0.0.1 故障代理、RSS 采样/内存判定、窗口/指标/流程模块及其测试
- forest_mob_render_test 输出 PASS/FAIL 标记，供 rendering_batch_test.sh 识别
- 新增 docs/FIRST-MAC-PLAYABLE-STATUS.md：如实记录 PASS/BLOCKED、已知问题与环境需求
- .gitignore 排除本地场景配置、凭据文件与运行输出

离线回归：rendering_batch_test.sh failures=0，playable_gate_test.sh PASS，
node 夹具测试 PASS。未联网运行，未重建候选包。

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ft3kXpNdLbKEfg5uDLfqVF

project/target_effect_test.gd

@@ -54,6 +54,27 @@ func run() -> void:
 	target.free()
 	game._on_local_motion_event_detailed({"type": 10, "effect": "full/path.mse", "sound": "", "pos": Vector3.ZERO})
 	check(registry.seen.size() == 1, "despawned target not replaced by caster")
+	game._on_skill_cast_started(1, 0)
+	game._on_local_motion_event_detailed({"type": 10, "effect": "full/path.mse", "sound": "", "pos": Vector3.ZERO})
+	check(registry.seen.size() == 1, "cast without a target spawns no target effect")
+	# A following effect whose target dies/despawns mid-life is freed, never left at a stale position.
+	var victim := Node3D.new()
+	root.add_child(victim)
+	var outside := Node3D.new()
+	var outside_anchor := Anchor.new()
+	check(not outside_anchor.configure(outside, Vector3.ZERO, true), "target outside the tree is rejected")
+	outside_anchor.free()
+	outside.free()
+	var follower := Node3D.new()
+	root.add_child(follower)
+	var follow_anchor := Anchor.new()
+	follower.add_child(follow_anchor)
+	check(follow_anchor.configure(victim, Vector3.ZERO, true), "follower configured")
+	var follower_ref: WeakRef = weakref(follower)
+	victim.free()
+	await process_frame
+	await process_frame
+	check(follower_ref.get_ref() == null, "follower freed after its target left the tree")
 	game.free()
 	effect.free()
 	await process_frame