CLI: add --exit-code to stale command

[shouryasrivastava]

Summary

• add an optional --exit-code flag to hflow stale
• return status 1 when stale episodes are found while preserving the default pipe-friendly status
• add regression coverage for stale and current catalogs
• document CI gating usage

Closes #30

Validation

• uv run pytest -q tests/test_catalog_curation.py -k cli_stale (4 passed)
• uv run ruff check
• uv run ruff format --check
• uv run ty check
• uv run pytest -q -k "not test_env_override_wins" (305 passed, 6 skipped)

The unfiltered full suite has one unrelated host-specific failure: test_env_override_wins expects /usr/bin/ffmpeg, which is absent on macOS. No ffmpeg code or tests are changed by this PR.

[github-actions]

👋 Hi @shouryasrivastava — thank you so much for your first contribution to HFlow!

A maintainer will review your pull request as soon as possible. In the meantime:

• ⭐ Star the repo: https://github.com/Hebbian-Robotics/hflow
• 💬 Join our Discord: https://discord.gg/vacepQvjmg
• 📖 Check CONTRIBUTING.md for the validation commands CI will run
• 📣 Share the project with your network

💡 Tip: one open pull request per contributor at a time. Issues with an assignee are taken; everything else is fair game.

We are excited to have you here and appreciate your help making the project better! 🙌

[kstonekuan]

Thank you @shouryasrivastava, and sorry for the outcome here: #30 was already assigned to @chiruu12 before this pull request opened. They asked for it, laid out a plan, and I told them it was theirs, so I owe them the chance to land it. That is the only reason I am closing this, and it is not a judgment on your work. The description is thorough, you covered both the stale and up-to-date cases, and you documented the CI usage, which is what the issue asked for.

Our convention, for next time: an issue with an assignee is taken. Anything without one is fair game, including issues that already have a linked pull request. The assignee list is the only signal that reserves an issue, so it is worth a quick look before starting.

Nothing is lost here. If @chiruu12 does not land it, I will come back and ask you to reopen this.

In the meantime there are plenty of unassigned good first issues. Since you clearly know your way around the CLI, these three are close to what you just did and are all unclaimed right now:

• CLI: hflow down, ingest, and status print a bare --help with no description #61: hflow down, ingest, and status print a bare --help with no description
• Tests: hflow ingest rejection of non-relative URIs has no coverage #67: the hflow ingest guard against non-relative URIs has no test
• Tests: hflow stale --pipeline with no App variable has no coverage #68: hflow stale --pipeline with no App variable has no test

Come say hi on Discord too, and thank you for jumping in.

[kstonekuan]

Following up as promised: @chiruu12 landed #30 in #81, so there is nothing to reopen here. Thank you again for the work and for taking the outcome gracefully.

The three I pointed you at are all still unclaimed if you want one: #61 (down/ingest/status have no --help description), #67 (no test for the ingest non-relative-URI guard), and #68 (no test for stale --pipeline with no App). Happy to assign you one so it is reserved before you start, just say which.