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/CHANGELOG.md

@@ -2,6 +2,74 @@
 
 ## [Unreleased]
 
+### Added
+- **v0.2 PR #1 — Postgres migration**: production backing store switched from
+  SQLite to PostgreSQL 16 ahead of M8-Py (FastAPI) per DR-2.
+  - `pyproject.toml`: `asyncpg>=0.30` + `psycopg[binary]>=3.2` +
+    `langgraph-checkpoint-postgres>=2.0.0` added to runtime; `aiosqlite>=0.20`
+    moved to `[dependency-groups].dev` (test-only); `langgraph-checkpoint-sqlite`
+    removed.
+  - `src/my_deepagent/persistence/db.py`: dialect-aware connect listener —
+    SQLite still gets `WAL` + `busy_timeout=5000` + `foreign_keys=ON`, Postgres
+    gets `SET TIME ZONE 'UTC'`. New `Database.dialect_name` property + `drop_schema`
+    method for tests.
+  - `src/my_deepagent/persistence/checkpointer.py`: `SqliteSaver` →
+    `AsyncPostgresSaver`. API is now async (`async with`) and takes a
+    connection string; SQLAlchemy URL prefixes (`postgresql+asyncpg://`,
+    `postgresql+psycopg://`) are auto-stripped to a plain libpq DSN. New
+    `_to_psycopg_dsn` helper covered by 4 unit tests.
+  - `src/my_deepagent/persistence/upsert.py` (new): `insert_for(session)` —
+    dialect-aware UPSERT helper. Picks `postgresql.insert` or `sqlite.insert`
+    based on the bound engine's dialect. Replaces 5 hardcoded `sqlite_insert`
+    call sites in `budget.py`, `recovery.py`, and `cli/doctor.py`.
+  - `src/my_deepagent/config.py`: `database_url` default switched from
+    `sqlite+aiosqlite:///<data_dir>/database.sqlite3` to
+    `postgresql+asyncpg://devflow:devflow@localhost:55432/mydeepagent`. The v3
+    `devflow` DB is preserved untouched; v4 lives in a fresh `mydeepagent` DB.
+  - `src/my_deepagent/persistence/models.py`: `RunRow.__table_args__` partial
+    unique index now declares **both** `postgresql_where=` and `sqlite_where=`
+    so the index is partial on both dialects.
+  - `src/my_deepagent/cli/doctor.py`: check 8 (`disk+db`) is now dialect-aware
+    — Postgres path runs `SELECT 1` (pg_isready equivalent: proves
+    reachability + auth + DB exists); SQLite path keeps
+    `PRAGMA integrity_check`. Doctor docstring updated.
+  - `alembic/env.py`: env-aware URL resolution — `MYDEEPAGENT_DATABASE_URL` >
+    `DATABASE_URL` > Postgres default. Async driver prefixes
+    (`+asyncpg`, `+aiosqlite`) are mapped to the sync equivalents alembic
+    needs (`+psycopg`, plain `sqlite`).
+  - `alembic/versions/9f2a6c79667e_v0_2_baseline_schema_postgres.py` (new):
+    fresh baseline autogenerated against live Postgres. Old SQLite baseline
+    `79945fdc2649` + partial-index migration `839f2233e346` deleted.
+  - `tests/conftest.py` (new): `pg_db_url` async fixture. Creates a fresh
+    Postgres database per test (against docker-compose `devflow-postgres`)
+    via the maintenance `postgres` DB; drops on teardown after terminating
+    any lingering backends. Used by the E2E suite and the new checkpointer
+    tests.
+  - `tests/integration/test_checkpointer.py`: rewritten for AsyncPostgresSaver
+    (4 pure DSN-converter tests + 3 async context-manager tests).
+  - `tests/integration/test_e2e_workflow.py`: switched from `sqlite+aiosqlite`
+    tmp_path to `pg_db_url`. Real OpenRouter E2E now exercises the production
+    Postgres path end-to-end (~122 s, ~$0.05/run).
+
+### Migration trigger (per DR-2)
+- The bound is *two concurrent writers* on `runs` / `run_phases` / `llm_calls`.
+  Today the CLI is the only writer — but M8-Py (FastAPI) introduces a second
+  one, and SQLite WAL allows only a single concurrent writer. Doing the move
+  *before* M8-Py lands gives the test surface time to harden.
+- Recovery: previous SQLite database at
+  `~/Library/Application Support/my-deepagent/database.sqlite3` (macOS) /
+  `$XDG_DATA_HOME/my-deepagent/database.sqlite3` is **not migrated** —
+  v0.1.0 was the only release that wrote to it and v0.2 starts a fresh
+  history. Set `MYDEEPAGENT_DATABASE_URL=sqlite+aiosqlite:///<path>` to
+  read the legacy file if needed.
+
+### Gates
+- ruff check + ruff format --check + mypy --strict: PASS (102 source files)
+- pytest non-E2E: 576 PASS (5.46 s) — bulk on sqlite tmp_path, new
+  checkpointer suite on Postgres `pg_db_url`
+- pytest E2E real OpenRouter: 1 PASS (122.93 s) on Postgres backend
+
+
 ## [0.1.0] - 2026-05-16
 
 First tagged milestone of the Python rewrite. The pre-Python-rewrite TypeScript