validate(): extract resume-file parsing into a named helper

[hallerite]

Summary

Addresses @snimu's readability feedback on the resume block in TaskSet.validate() — the previous code was a three-level nested for/try/if chain inline, which obscured the simple intent ("parse prior JSONL, filter to in-range indices").

Changes

verifiers/envs/experimental/composable/task.py:

• Pulls the resume-file reader into a local helper _read_prior_rows(path) -> (rows, indices) with a brief docstring explaining the in-range filter rationale.

• Top-level resume flow is now flat and reads top-to-bottom:

  if resume and out_path_p.exists():
      prior_rows, completed_indices = _read_prior_rows(out_path_p)
      if prior_rows:
          logger.info("Resuming: %d rows already in %s, will skip", ...)
  else:
      out_path_p.write_text("")

No behavior change

Helper preserves existing semantics:

• Only rows whose index is in [0, total) are kept — resuming with a smaller n than a prior run still doesn't leak out-of-range rows into the result list or summary stats.
• Blank / non-JSON lines and rows without an integer index are silently skipped (same as before).
• Returns (rows, indices) so the main loop's todo filter keeps working unchanged.

Test plan

• ruff check / ruff format --check clean
• CI

🤖 Generated with Claude Code

---

Note

Low Risk
Low risk refactor confined to TaskSet.validate() resume handling; intended behavior is preserved but could affect edge cases around malformed JSONL or index filtering if incorrect.

Overview
Refactors TaskSet.validate() resume logic by extracting prior JSONL parsing into a local _read_prior_rows() helper with a docstring, reducing nested control flow.

Resume behavior remains the same: it reads existing out_path JSONL, filters to in-range integer index values (< total), skips malformed/blank lines, and returns both prior_rows and completed_indices for subsequent validation and logging.

^{Reviewed by Cursor Bugbot for commit 8c14c2e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[snimu]

can we move the logging into the helper as well?

[hallerite]

Done in 8c14c2e — moved the logger.info(...) inside the helper, so the caller no longer reaches back for len(prior_rows). Docstring also mentions the log side-effect.