feat: record the observability fields end to end through telemetry

src/polygateway/telemetry/sqlite.py

@@ -34,10 +34,16 @@ CREATE TABLE IF NOT EXISTS llm_calls (
     cache_hit          INTEGER NOT NULL DEFAULT 0,
     error              TEXT,
     cost               REAL,
-    created_at         TEXT    NOT NULL DEFAULT (datetime('now'))
+    created_at         TEXT    NOT NULL DEFAULT (datetime('now')),
+    cached_prompt_tokens INTEGER,
+    model_reported       TEXT
 );
 """
 
+# 新列必须排在 created_at 之后: 旧表只能经 ALTER 追加到末尾,新建库若把它们
+# 插在前面,两条路径的物理列序会分叉(列序断言测试无合规修法)。
+_BACKFILL_COLUMNS = (("cached_prompt_tokens", "INTEGER"), ("model_reported", "TEXT"))
+
 _COLUMNS = (
     "call_id",
     "parent_call_id",
@@ -57,6 +63,8 @@ _COLUMNS = (
     "cache_hit",
     "error",
     "cost",
+    "cached_prompt_tokens",
+    "model_reported",
 )
 
 _INSERT = (
@@ -82,9 +90,32 @@ class SQLiteRecorder:
             self._conn = conn
         except (OSError, sqlite3.Error) as exc:
             logger.warning("SQLite 遥测初始化失败,后续记录降级为 no-op: {}", exc)
+        self._backfill_columns()
+
+    def _backfill_columns(self) -> None:
+        """给已存在的旧表补新列(issue #3);独立 try,失败只降级为逐行丢弃。
+
+        必须放在 `self._conn` 赋值**之后**并先判空: 初始化失败时连接为 None,
+        无守卫的补列会抛 AttributeError 逃出 `__init__`,把"静默降级"变成崩溃。
+        补列失败也绝不清空 `self._conn`——那会让整个 recorder 永久 no-op,
+        比逐行丢弃严重得多。
+        """
+        if self._conn is None:
+            return
+        try:
+            existing = {row[1] for row in self._conn.execute("PRAGMA table_info(llm_calls)")}
+            for column, decl in _BACKFILL_COLUMNS:
+                if column in existing:
+                    continue
+                self._conn.execute(f"ALTER TABLE llm_calls ADD COLUMN {column} {decl}")
+            self._conn.commit()
+        except sqlite3.Error as exc:
+            # duplicate column: 多进程共库时后到者必然撞上,属预期竞态,视为成功
+            if "duplicate column" not in str(exc).lower():
+                logger.warning("SQLite 遥测补列失败(写入将逐行降级): {}", exc)
 
     async def record_llm_call(self, **fields: object) -> None:
-        """写一行遥测;字段集合即 18 字段冻结签名(ports.TelemetryRecorder)。"""
+        """写一行遥测;字段集合即 20 字段冻结签名(ports.TelemetryRecorder)。"""
         if self._conn is None:
             return
         row = tuple(fields[col] for col in _COLUMNS)