* fix: universal tool_call/tool_result orphan detection for OpenAI-compat providers
The Anthropic provider had orphan detection for mismatched tool_call ↔
tool_result pairs, but OpenAI-compatible providers (Chat Completions,
Google, Responses API) had none. When an Anthropic model runs behind
an OpenAI-compat API (e.g. Azure) or cancellation creates orphans,
the API rejects the malformed request.
- Rewrite sanitize_messages() with orphan detection: synthesize error
tool results for unmatched tool_calls, drop tool results with no
matching tool_call, fill empty tool_call IDs with positional remap
- Call sanitize_messages() from Responses API _convert_messages()
* fix: address review feedback on orphan detection
- Track answered IDs per-turn (local_answered) instead of scanning
all of out, preventing false matches from reused IDs across turns
- Drop empty-ID tool results that have no remap entry instead of
passing them through with invalid empty tool_call_id
- Increment empty_result_idx for every empty result, not just remapped
- Remove dead result_ids peek-ahead code
- Add test for repeated tool_call IDs across turns
Patrick Buckley
50e6e64c3d