FLAG-1 unified task_attempts schema (single canonical DDL + 3-shape migration)

User decision 2026-11-05: unified schema, rejecting the rehearsal
runtime column-union workaround and a ledger rename. One definition
(cloud.attempt_ledger.TASK_ATTEMPTS_DDL, 12 columns) shared by
cloud.attempts and cloud.db.POSTGRES_SCHEMA; ensure builds the
unified table fresh and migrates old resume, gap-3 ledger, and
rehearsal shapes in place with rows intact. aggregate counts
ledger rows only (outcome NULL = resume row, never counted).
SQLite verified by 8 new tests; Postgres real-DB upgrade path
explicitly NOT verified (see batch summary). Local commit only:
no merge, no push, no deploy.

cloud/db.py

@@ -65,6 +65,12 @@ import time
 from abc import ABC, abstractmethod
 from contextlib import contextmanager
 
+# 统一 schema：task_attempts 的 PG 新库定义与台账定义是同一
+# 字符串（cloud.attempt_ledger.TASK_ATTEMPTS_DDL），不在此另
+# 写一份。attempt_ledger 只依赖标准库 time，与本模块无循环
+# 导入；层规则上它也不属于 orchestration 模块集合。
+from cloud.attempt_ledger import TASK_ATTEMPTS_DDL as _TASK_ATTEMPTS_DDL
+
 # 与 server.py 旧 _connect 的 timeout=30s 保持一致的连接级等待；
 # PRAGMA busy_timeout 是语句级等待，两者不冲突，后者以毫秒为单位
 # 在每个连接上单独设置（不随库文件持久化，见 connect 的注释）。
@@ -876,18 +882,11 @@ POSTGRES_SCHEMA = (
     "created_at DOUBLE PRECISION)",
     "CREATE INDEX IF NOT EXISTS idx_task_steps_task"
     " ON task_steps(task_id, step_no)",
-    # 尝试账本（v6，见 cloud/attempts.py）：(task_id, attempt_no)
-    # 唯一；PG 新库一次建齐，老库走 server/worker ensure。
-    "CREATE TABLE IF NOT EXISTS task_attempts("
-    "task_id TEXT, "
-    "attempt_no INTEGER, "
-    "kind TEXT, "
-    "interrupted_reason TEXT, "
-    "checkpoint_round INTEGER, "
-    "result_text TEXT, "
-    "error_text TEXT, "
-    "created_at DOUBLE PRECISION, "
-    "PRIMARY KEY(task_id, attempt_no))",
+    # 尝试账本（统一 schema，见 cloud/attempt_ledger.py）：
+    # (task_id, attempt_no) 唯一；PG 新库一次建齐，老库走
+    # server/worker ensure 迁移到同一列集。此处是导入的统
+    # 一定义本身，不是第二份 DDL。
+    _TASK_ATTEMPTS_DDL,
     # 审计循环状态（audit loop）：task_id 单行主键；PG 新库一次
     # 建齐，老库走 server/worker ensure（见 cloud/audit_loop.py）。
     "CREATE TABLE IF NOT EXISTS task_audit_loop_state("