[mikemikimike]

Summary

• degrade optional stage calls only for HTTP 404 responses
• surface authentication, authorization, rate-limit, 5xx, and statusless Airflow failures through the existing sanitized 502 response
• add deterministic regression coverage for stage DAG listing, task-instance listing, and recent-run listing

Tests

• uv run --locked pytest -q: 1252 passed, 8 skipped
• uv run --locked ruff check
• uv run --locked ruff format --check
• uv run --locked ty check

[github-actions]

👋 Hi @mikemikimike — thanks for the contribution! To keep starter issues available
for other contributors and give every pull request a real review, we accept
1 open pull request per contributor at a time.

You already have #328 open, so this one is being closed automatically.
Once your open pull request is merged or closed, feel free to reopen this one —
no work is lost.