Normalize checkpoint success flags and identifier handling to fix resume behavior

[hemanth-asirvatham]

Motivation

• Resuming long runs could fail to detect completed rows when the Successful column was stored as strings (e.g. "True", "true", "1"), causing already-done rows to be reprocessed.
• Identifier type mismatches (numeric vs string) also prevented correct deduplication and resume logic.
• Make resume/checkpoint detection robust to hand-edited or legacy CSVs so partially completed runs reliably continue from checkpoints.

Description

• Normalize the Successful column when loading a saved CSV by coercing boolean-like values and matching common success strings ("true", "1", "yes", "completed", etc.) before building the done set; change located in src/gabriel/utils/openai_utils.py.
• Normalize identifier handling to string form when computing done, filtering todo_pairs, and during write-time deduplication so comparisons are type-consistent; updates in src/gabriel/utils/openai_utils.py.
• Ensure written_identifiers stores string identifiers and use astype(str) when checking batch_df to avoid reappends of already-saved rows; updates in src/gabriel/utils/openai_utils.py.
• Add a regression test test_resume_treats_string_success_values_as_completed to tests/test_reset_files.py that seeds a checkpoint CSV with string-valued Successful entries and verifies reset_files=False resumes without reprocessing those rows.

Testing

• Ran pytest -q tests/test_reset_files.py tests/test_openai_dummy.py and both tests suites passed locally (6 passed for the two test files run).
• The new regression test confirms previously failing behavior (string success flags treated as incomplete) is resolved.

---

Codex Task

[github-actions]

Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

---

I have read the CLA Document and I hereby sign the CLA

---

_{You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.}