chore: pre-feature cleanup — regression baseline, config landmines, logging/serialization hygiene

[kevinmenear]

What / Why

Before starting the jobs-data input feature (changing FastSim's input from raw SLURM dumps to a jobs-data format), clean up known landmines and establish the regression safety net the refactor depends on. All items below were verified against the code on feature/jobs-data-input (see dev/202607062252-determinism-check.md for the determinism verification this builds on).

Subtasks

Regression safety net (do first)

• Promote the canonicalized results-comparison script into the repo as scripts/compare_results.py (canonicalizes set order, compares Jobs by jid, handles enums/MappingProxyType, depth-capped recursion — see dev note for rationale)
• Capture and document a baseline results pickle for a reference config so future refactors can diff against it

Bugs / landmines

• Add a default for save_interval_steps in scheduler/config.py — controller.py:750 reads it unconditionally and a YAML that omits it crashes mid-run
• Fix U+2010 unicode hyphen in skip reason "NOT-ENOUGH-NODES‐NOW" (controller.py:1212) — lands in wait_history output and breaks ASCII matching
• Replace the seven bare except: blocks in controller.py (lines 771, 888, 937, 1417, 1488, 1530, 1711) with specific exceptions or at least logged failures

Hygiene

• Fix hardcoded log dir '../' in main.py:246 — with repo-root CWD convention, logs scatter into the repo's parent; derive from output path or default to ./logs
• Deduplicate job-history serialization (checkpoint path controller.py:752-775 vs final save main.py:257-278) into one function
• Open the power log once at init instead of re-checking/reopening the CSV every simulation step (controller.py:2185+)
• Remove duplicate re_fp key in configs/kestrel_conf.yaml (lines 40-41; YAML silently keeps the second, "")
• Add *.zip to .gitignore (power_data.zip / slurm_dump.zip, ~108 MB, currently one git add . from being committed)

Deferred (fold into jobs-data input feature design)

• Output format: stop pickling live simulator objects (Dependency, JobState, Job refs) — results pickles currently require scheduler/ importable to load

Notes

• Determinism of the simulator was verified 2026-07-06: two identical 3-day Kestrel runs produce identical job histories after canonicalization (dev/202607062252-determinism-check.md).
• Work happens on a branch off feature/jobs-data-input, PR'd back into that branch, one commit per subtask where practical.