feat(my-deepagent): v0.2 PR #1 — Postgres migration (ahead of M8-Py FastAPI)

Switches the production backing store from SQLite to PostgreSQL 16, per DR-2.
The migration trigger is two concurrent writers on the my-deepagent ORM
tables — which first appears with FastAPI (M8-Py). Doing the cut now keeps
the surface area small while M8-Py is still planning.

Production deps: `asyncpg`, `psycopg[binary]`, `langgraph-checkpoint-postgres`.
Test deps: `aiosqlite` (the bulk of unit + integration tests stay on sqlite
tmp_path for speed; the E2E suite and the new checkpointer tests exercise
the live Postgres path).

Highlights
- `persistence/db.py`: dialect-aware connect listener. SQLite still gets
  WAL + busy_timeout=5000 + foreign_keys=ON; Postgres gets `SET TIME ZONE 'UTC'`.
  Added `Database.dialect_name` + `drop_schema` (test-only).
- `persistence/checkpointer.py`: SqliteSaver → AsyncPostgresSaver. API is
  now async (`async with`) and takes a connection string. SQLAlchemy URL
  prefixes (`+asyncpg`, `+psycopg`) are auto-stripped to a plain libpq DSN
  (`_to_psycopg_dsn` helper, 4 unit tests).
- `persistence/upsert.py` (new): `insert_for(session)` — dialect-aware UPSERT
  helper. Picks `postgresql.insert` or `sqlite.insert` based on the bound
  engine. Replaces 5 hardcoded `sqlite_insert` call sites in `budget.py`,
  `recovery.py`, `cli/doctor.py`.
- `persistence/models.py`: `RunRow` partial unique index declares both
  `postgresql_where=` and `sqlite_where=` for cross-dialect correctness.
- `config.py`: default `database_url` now
  `postgresql+asyncpg://devflow:devflow@localhost:55432/mydeepagent`. v3
  `devflow` DB preserved untouched; v4 lives in a fresh `mydeepagent` DB.
- `cli/doctor.py` check 8: dialect-aware DB liveness probe. Postgres path
  runs `SELECT 1` (pg_isready equivalent); SQLite keeps `PRAGMA integrity_check`.
- `alembic/env.py`: env-aware URL resolution (`MYDEEPAGENT_DATABASE_URL` >
  `DATABASE_URL` > default). Async driver prefixes are mapped to the sync
  equivalents alembic needs.
- `alembic/versions/9f2a6c79667e_v0_2_baseline_schema_postgres.py` (new):
  fresh baseline autogenerated against live Postgres. Old SQLite migrations
  (`79945fdc2649`, `839f2233e346`) deleted — v0.2 starts a clean history.
- `tests/conftest.py` (new): `pg_db_url` async fixture creates a fresh DB
  per test against docker-compose `devflow-postgres` and drops it on
  teardown after terminating lingering backends.
- `tests/integration/test_checkpointer.py`: rewritten for AsyncPostgresSaver
  (4 pure DSN-converter unit tests + 3 async context-manager integration tests).
- `tests/integration/test_e2e_workflow.py`: switched to `pg_db_url`. Real
  OpenRouter E2E now exercises the production Postgres path end-to-end.

Recovery
- Previous SQLite database at the platformdirs data_dir is NOT auto-migrated;
  v0.1.0 was the only release that wrote to it. Set
  `MYDEEPAGENT_DATABASE_URL=sqlite+aiosqlite:///<path>` to read it.
- The v3 `devflow` Postgres DB is preserved untouched (separate database
  name); to inspect: `psql -h localhost -p 55432 -U devflow -d devflow`.

Gates
- ruff check + ruff format --check + mypy --strict: PASS (102 source files)
- pytest non-E2E: 576 PASS (5.46 s)
- pytest E2E real OpenRouter on Postgres: 1 PASS (122.93 s, ~$0.05/run)

--no-verify: lefthook still TS-only (deleted in 0e61b2d but still queryable
in git history).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

my-deepagent/src/my_deepagent/cli/doctor.py

@@ -8,7 +8,7 @@ Checks:
   5. config + governance consent
   6. OpenRouter API key reachable
   7. OpenRouter /models ping + pricing matrix upsert
-  8. Disk free + SQLite integrity_check
+  8. Disk free + DB liveness probe (pg `SELECT 1` / sqlite `PRAGMA integrity_check`)
 """
 
 from __future__ import annotations
@@ -26,7 +26,6 @@ import typer
 from rich.console import Console
 from rich.table import Table
 from sqlalchemy import text as sa_text
-from sqlalchemy.dialects.sqlite import insert as sqlite_insert
 
 from ..config import Config, load_config
 from ..errors import MyDeepAgentError
@@ -38,6 +37,7 @@ from ..monitoring.pricing import (
 )
 from ..persistence.db import Database
 from ..persistence.models import ModelPricingRow
+from ..persistence.upsert import insert_for
 from ..secrets import resolve_openrouter_api_key
 
 _CONSOLE = Console()
@@ -147,9 +147,10 @@ async def _upsert_pricing(config: Config, prices: list[ModelPrice]) -> None:
     now = datetime.now(UTC).isoformat(timespec="seconds")
     try:
         async with db.session() as s:
+            insert = insert_for(s)
             for p in prices:
                 stmt = (
-                    sqlite_insert(ModelPricingRow)
+                    insert(ModelPricingRow)
                     .values(
                         model=p.model,
                         input_per_1k_usd=p.input_per_1k_usd,
@@ -175,6 +176,12 @@ async def _upsert_pricing(config: Config, prices: list[ModelPrice]) -> None:
 
 
 async def _check_disk_and_db(config: Config) -> CheckResult:
+    """Disk free + DB liveness probe.
+
+    Postgres path: ``SELECT 1`` round-trip (pg_isready equivalent — proves
+    network reachability, auth, and that the DB exists).
+    SQLite path: ``PRAGMA integrity_check`` to detect corruption.
+    """
     usage = shutil.disk_usage(str(config.workspace_root))
     free_gb = usage.free / (1024**3)
     if free_gb < 2.0:
@@ -185,15 +192,34 @@ async def _check_disk_and_db(config: Config) -> CheckResult:
         disk_status = "ok"
 
     db = Database(config.database_url)
-    await db.init_schema()
+    db_detail = ""
+    db_ok = False
     try:
+        # init_schema is idempotent and safe; for Postgres it requires CREATE
+        # privileges, which the default devflow role has on the mydeepagent DB.
+        # If alembic has already been applied this is a no-op.
+        await db.init_schema()
         async with db.session() as s:
-            row = (await s.execute(sa_text("PRAGMA integrity_check"))).scalar_one()
+            if db.dialect_name == "postgresql":
+                # pg_isready-equivalent: simple round-trip query proves the
+                # server is reachable, auth works, and the DB exists.
+                row = (await s.execute(sa_text("SELECT 1"))).scalar_one()
+                db_ok = row == 1
+                db_detail = f"postgres_alive={'ok' if db_ok else 'fail'}"
+            elif db.dialect_name == "sqlite":
+                row = (await s.execute(sa_text("PRAGMA integrity_check"))).scalar_one()
+                db_ok = row == "ok"
+                db_detail = f"sqlite_integrity={'ok' if db_ok else str(row)}"
+            else:  # pragma: no cover — defensive for future dialects
+                db_ok = True
+                db_detail = f"dialect={db.dialect_name},probe=skipped"
+    except Exception as e:
+        db_ok = False
+        db_detail = f"db_error={type(e).__name__}:{e}"
     finally:
         await db.dispose()
 
-    db_ok = row == "ok"
-    detail = f"free={free_gb:.1f}GB, sqlite_integrity={'ok' if db_ok else str(row)}"
+    detail = f"free={free_gb:.1f}GB, {db_detail}"
     if disk_status == "fail" or not db_ok:
         final: Literal["ok", "warn", "fail"] = "fail"
     elif disk_status == "warn":