Move sqlite logs to a dedicated database (#13772)

## Summary
- move sqlite log reads and writes onto a dedicated `logs_1.sqlite`
database to reduce lock contention with the main state DB
- add a dedicated logs migrator and route `codex-state-logs` to the new
database path
- leave the old `logs` table in the existing state DB untouched for now

## Testing
- just fmt
- cargo test -p codex-state

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/state/logs_migrations/0001_logs.sql

@@ -0,0 +1,21 @@
+CREATE TABLE logs (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    ts INTEGER NOT NULL,
+    ts_nanos INTEGER NOT NULL,
+    level TEXT NOT NULL,
+    target TEXT NOT NULL,
+    message TEXT,
+    module_path TEXT,
+    file TEXT,
+    line INTEGER,
+    thread_id TEXT,
+    process_uuid TEXT,
+    estimated_bytes INTEGER NOT NULL DEFAULT 0
+);
+
+CREATE INDEX idx_logs_ts ON logs(ts DESC, ts_nanos DESC, id DESC);
+CREATE INDEX idx_logs_thread_id ON logs(thread_id);
+CREATE INDEX idx_logs_process_uuid ON logs(process_uuid);
+CREATE INDEX idx_logs_thread_id_ts ON logs(thread_id, ts DESC, ts_nanos DESC, id DESC);
+CREATE INDEX idx_logs_process_uuid_threadless_ts ON logs(process_uuid, ts DESC, ts_nanos DESC, id DESC)
+WHERE thread_id IS NULL;