feat(sense): T-G0 语义分析器骨架（包结构/DDL/灰度门控挂载）

- gateway/sense/：config（SenseConfig：mode 灰度三态/特征门/conformal/consumers
  档位映射，mode 非法回落 collect）、errors（EmbedderDown/ArtifactMissing，D-G4 降级）、
  store（tier_observations + sense_artifacts DDL，WAL；观察写入/标签回填/
  labeled 查询/180d 清理/工件登记与 active 切换）、routes（/sense/health 透出灰度状态）
- settings DEFAULTS 增 sense 段（enabled 默认 False，mode 默认 collect——D-G7）
- api.py include_router 门控（装配失败不拖垮主应用）
- 测试 +5：门控 404/DDL 幂等/配置缺省与 mode 回落/独立挂载 health/
  观察写入-回填-计数-清理链路，全量 375 passed

gateway/sense/config.py

@@ -0,0 +1,90 @@
+"""SenseConfig：从 settings 的 sense 段构建语义分析器配置（T-G0）。
+
+灰度纪律（D-G7）：
+- enabled 默认 False（总开关，关闭时不注册任何 /sense 或 /v1/route 路由）；
+- mode 默认 "collect"（只记不决策）；collect 攒满 min_labels 前禁止 live
+  （晋升校验在 grader/admin，配置层不阻止写值——但 admin promote 会复核）。
+"""
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import Any, Dict
+
+MODES = ("collect", "shadow", "live")
+
+
+@dataclass
+class EmbedderCfg:
+    base_url: str = "http://127.0.0.1:8902/v1"
+    model: str = "bge-m3-Q4_K_M"
+    timeout_s: float = 5.0
+    dim: int = 1024
+
+
+@dataclass
+class SenseConfig:
+    enabled: bool = False
+    mode: str = "collect"                    # collect | shadow | live
+    db_path: str = "data/sense.sqlite3"
+    admin_key: str = ""
+    embedder: EmbedderCfg = field(default_factory=EmbedderCfg)
+    t1_max_tokens: int = 512
+    t1_max_turns: int = 2
+    intent_blacklist: tuple = ("重构", "脚手架", "迁移", "实现", "多文件", "项目")
+    code_t1_kinds: tuple = ("解释", "补全")
+    alpha: float = 0.05
+    min_labels: int = 500
+    t2_prefer_local_when_idle: bool = True
+    consumers: Dict[str, Dict[str, str]] = field(default_factory=lambda: {
+        "proxy": {"t1": "local-small", "t2": "budget", "t3": "premium"}})
+    models_dir: str = "data/sense_models"
+    retention_days: int = 180
+
+    def tier_pool_hint(self, consumer: str, tier: str) -> str:
+        """消费方×档位 -> model_pool 档位名（§5 consumers；缺省兜底 local/budget/premium）。"""
+        m = self.consumers.get(consumer) or {}
+        return m.get(tier) or {"t1": "local", "t2": "budget",
+                               "t3": "premium"}.get(tier, "budget")
+
+
+def build_sense_config(settings_dict: Dict[str, Any]) -> SenseConfig:
+    """从 settings.to_dict() 的 sense 段构建（缺省兜底；mode 非法回落 collect）。"""
+    raw = settings_dict.get("sense") or {}
+    if not isinstance(raw, dict):
+        raw = {}
+    emb = raw.get("embedder") or {}
+    if not isinstance(emb, dict):
+        emb = {}
+    feats = raw.get("features") or {}
+    if not isinstance(feats, dict):
+        feats = {}
+    policy = raw.get("policy") or {}
+    if not isinstance(policy, dict):
+        policy = {}
+    consumers = raw.get("consumers") or {}
+    if not isinstance(consumers, dict):
+        consumers = {}
+    mode = str(raw.get("mode", "collect") or "collect")
+    if mode not in MODES:
+        mode = "collect"
+    return SenseConfig(
+        enabled=bool(raw.get("enabled", False)),
+        mode=mode,
+        db_path=str(raw.get("db_path") or "data/sense.sqlite3"),
+        admin_key=str(raw.get("admin_key") or ""),
+        embedder=EmbedderCfg(
+            base_url=str(emb.get("base_url") or "http://127.0.0.1:8902/v1"),
+            model=str(emb.get("model") or "bge-m3-Q4_K_M"),
+            timeout_s=float(emb.get("timeout_s", 5) or 5),
+            dim=int(emb.get("dim", 1024) or 1024),
+        ),
+        t1_max_tokens=int(feats.get("t1_max_tokens", 512) or 512),
+        t1_max_turns=int(feats.get("t1_max_turns", 2) or 2),
+        intent_blacklist=tuple(feats.get("intent_blacklist")
+                               or ("重构", "脚手架", "迁移", "实现", "多文件", "项目")),
+        code_t1_kinds=tuple(feats.get("code_t1_kinds") or ("解释", "补全")),
+        alpha=float(policy.get("alpha", 0.05) or 0.05),
+        min_labels=int(policy.get("min_labels", 500) or 500),
+        t2_prefer_local_when_idle=bool(policy.get("t2_prefer_local_when_idle", True)),
+        consumers=consumers or SenseConfig().consumers,
+    )