feat: add debug clear-memories command to hard-wipe memories state (#13085)

#### 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

codex-rs/Cargo.lock

@@ -1603,6 +1603,7 @@ dependencies = [
  "codex-protocol",
  "codex-responses-api-proxy",
  "codex-rmcp-client",
+ "codex-state",
  "codex-stdio-to-uds",
  "codex-tui",
  "codex-utils-cargo-bin",
@@ -1614,6 +1615,7 @@ dependencies = [
  "pretty_assertions",
  "regex-lite",
  "serde_json",
+ "sqlx",
  "supports-color 3.0.2",
  "tempfile",
  "tokio",