[iris] Document priority bands and warn on PRODUCTION

[claude]

Add lib/iris/docs/priority-bands.md describing when to pick PRODUCTION, INTERACTIVE, or BATCH and the social contract for using PRODUCTION. CLI now logs a warning when --priority production is used so submitters know they are preempting other users' jobs.

Fixes #4747

[Helw150]

@claude remove all the CLI changes. Just change the docs.

[claude]

Claude finished @Helw150's task in 1m 59s —— View job

---

Task: Remove CLI changes, keep only docs

• Inspect current diff vs origin/main
• Revert changes to lib/iris/src/iris/cli/job.py
• Revert changes to lib/iris/tests/cli/test_job.py
• Drop the docs sentence that referenced the (now-removed) CLI warning
• Run ./infra/pre-commit.py --all-files --fix — passed
• Commit and push

Summary

PR now contains only documentation changes:

 lib/iris/OPS.md                 |  2 +-
 lib/iris/docs/priority-bands.md | 53 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 1 deletion(-)

The CLI warning behavior in lib/iris/src/iris/cli/job.py and its test in lib/iris/tests/cli/test_job.py were reverted to origin/main. I also removed the sentence in priority-bands.md that pointed at the CLI warning, since that behavior no longer exists.

Testing

I did not run uv run pytest because the CLI/test files are reverted to origin/main and the only remaining changes are Markdown docs, which have no tests to break. ./infra/pre-commit.py --all-files --fix passed (ruff, black, pyrefly, markdown, etc.).
• Branch: agent/20260414-fix-4747