## Summary
Generated memory rows and their stage-one/stage-two job state currently
live in `state_5.sqlite` alongside thread metadata. That makes memory
cleanup and regeneration share the main state schema even though those
rows are memory-pipeline data and can be rebuilt independently from the
durable thread records.
This PR moves the memory-owned tables into a dedicated
`memories_1.sqlite` runtime database while keeping thread metadata in
`state_5.sqlite`.
## Changes
- Adds a separate memories DB runtime, migrator, path helpers, telemetry
kind, and Bazel compile data for `state/memory_migrations`.
- Introduces `MemoryStore` behind `StateRuntime::memories()` and moves
memory table/job operations onto that store.
- Drops the old memory tables from the state DB and recreates their
schema in `state/memory_migrations/0001_memories.sql`.
- Updates memory startup, citation usage tracking, rollout pollution
handling, `debug clear-memories`, and app-server `memory/reset` to
operate through the memories DB.
- Preserves cross-DB behavior by hydrating thread metadata from the
state DB when selecting visible memory outputs and checking stage-one
staleness.
## Verification
- Added/updated `codex-state` tests for deleted-thread memory visibility
and already-polluted phase-two enqueue behavior.
- Updated `debug clear-memories`, app-server `memory/reset`, and
memories startup tests to seed and assert memory rows through
`memories_1.sqlite`.
## Why
`debug_clear_memories_resets_state_and_removes_memory_dir` can be flaky
because the test drops its `sqlx::SqlitePool` immediately before
invoking `codex debug clear-memories`. Dropping the pool does not wait
for all SQLite connections to close, so the CLI can race with still-open
test connections.
## What changed
- Await `pool.close()` before spawning `codex debug clear-memories`.
- Close the reopened verification pool before the temp `CODEX_HOME` is
torn down.
## Verification
- `cargo test -p codex-cli --test debug_clear_memories
debug_clear_memories_resets_state_and_removes_memory_dir`
#### what
adds a `codex debug clear-memories` command to help with clearing all
memories state from disk, sqlite db, and marking threads as
`memory_mode=disabled` so they don't get resummarized when the
`memories` feature is re-enabled.
#### tests
add tests
