Refactor snapshot bookkeeping into wrapper; add test output .gitignore

[lukstafi]

Summary

• Extract paired pop_snapshot()/snapshot_ch() calls from close_tree into a with_snapshot_bookkeeping wrapper in the PrintBox functor, making the save/restore boundary structural rather than positional (prevents regressions of the PR Fix toc file truncation during snapshot_every_sec #104 bug class)
• Add .gitignore patterns (debugger_*_debug*, *.raw) for generated test debug output files that were showing up as untracked

Test plan

• dune build compiles successfully
• dune runtest passes — all existing tests confirm behavior is preserved

🤖 Generated with Claude Code

[lukstafi]

@codex review Focus on bugs, correctness issues, and edge cases. Do not check adherence to a spec or plan.

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Another round soon, please!

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[lukstafi]

Retrospective — task-45c21e19

What went well

• Clean single-commit implementation, approved on first round with no action items.
• Codex automated review also found no issues.
• The proposal was precise enough that no deviation or investigation was needed.

What I'd do differently next time

• Nothing significant for this task. It was a small, well-scoped refactor with clear acceptance criteria. The proposal-to-implementation path was direct.

Possible follow-up improvements

• Consider making with_snapshot_bookkeeping exception-safe. The current wrapper does not call snapshot_ch if f () raises. In practice this is fine because snapshot() (the caller of close_log_impl ~from_snapshot:true) already has its own try/with that restores the stack on exception. However, a Fun.protect ~finally pattern would make the wrapper independently robust:

  let with_snapshot_bookkeeping ~from_snapshot f =
    pop_snapshot ();
    Fun.protect ~finally:(fun () ->
      if not from_snapshot then snapshot_ch ())
      f

  This is a judgment call — the extra safety may not be worth the complexity given the existing exception handling in snapshot(), but it would decouple the wrapper's correctness from its caller's behavior.