## Summary
This is a purely mechanical refactor of `OtelManager` ->
`SessionTelemetry` to better convey what the struct is doing. No
behavior change.
## Why
`OtelManager` ended up sounding much broader than what this type
actually does. It doesn't manage OTEL globally; it's the session-scoped
telemetry surface for emitting log/trace events and recording metrics
with consistent session metadata (`app_version`, `model`, `slug`,
`originator`, etc.).
`SessionTelemetry` is a more accurate name, and updating the call sites
makes that boundary a lot easier to follow.
## Validation
- `just fmt`
- `cargo test -p codex-otel`
- `cargo test -p codex-core`
This branch:
* Avoid flushing DB when not necessary
* Filter events for which we perfom an `upsert` into the DB
* Add a dedicated update function of the `thread:updated_at` that is
lighter
This should significantly reduce the DB lock contention. If it is not
sufficient, we can de-sync the flush of the DB for `updated_at`
## Summary
- add the v2 `thread/metadata/update` API, including
protocol/schema/TypeScript exports and app-server docs
- patch stored thread `gitInfo` in sqlite without resuming the thread,
with validation plus support for explicit `null` clears
- repair missing sqlite thread rows from rollout data before patching,
and make those repairs safe by inserting only when absent and updating
only git columns so newer metadata is not clobbered
- keep sqlite authoritative for mutable thread git metadata by
preserving existing sqlite git fields during reconcile/backfill and only
using rollout `SessionMeta` git fields to fill gaps
- add regression coverage for the endpoint, repair paths, concurrent
sqlite writes, clearing git fields, and rollout/backfill reconciliation
- fix the login server shutdown race so cancelling before the waiter
starts still terminates `block_until_done()` correctly
## Testing
- `cargo test -p codex-state
apply_rollout_items_preserves_existing_git_branch_and_fills_missing_git_fields`
- `cargo test -p codex-state
update_thread_git_info_preserves_newer_non_git_metadata`
- `cargo test -p codex-core
backfill_sessions_preserves_existing_git_branch_and_fills_missing_git_fields`
- `cargo test -p codex-app-server thread_metadata_update`
- `cargo test`
- currently fails in existing `codex-core` grep-files tests with
`unsupported call: grep_files`:
- `suite::grep_files::grep_files_tool_collects_matches`
- `suite::grep_files::grep_files_tool_reports_empty_results`
