fix: raise FerroStreamError on malformed streaming chunks

[MitulShah1]

Summary

Fixes the one open bug-labeled issue plus its sibling enhancement, both on the same code path:

• _stream() silently swallows malformed chunks (JSONDecodeError) #15 — _stream() silently swallowed malformed SSE chunks (except json.JSONDecodeError: continue), losing data with no error or log.
• Raise FerroStreamError in streaming error paths (currently never raised) #16 — FerroStreamError was defined and exported but never raised anywhere.

Both sync (completions/resource.py) and async (completions/async_resource.py) _stream() paths now raise FerroStreamError on a malformed chunk, with a truncated payload snippet and the original JSONDecodeError chained via raise ... from e. This is the first code path that actually raises FerroStreamError.

Also:

• Tightens test coverage flagged while reviewing Development #26: admin.plugins.list() {"plugins": [...]} wrapper branch, plus streaming malformed-chunk regression tests (sync + async).
• Adds .github/release.yml so GitHub's auto-generated release notes (the publish job already runs with generate_release_notes: true) group merged PRs by label and credit every contributor by @handle on each tagged release. Contributor credit lives in the release notes only — not in CHANGELOG.md.

Fixed Issues

Closes #15
Closes #16

Testing

• pytest tests/ — 67 passed (was 64).
• ruff check / ruff format --check — clean.
• mypy ferrolabsai — Success, no issues.
• .github/release.yml validated as well-formed YAML (10 categories).

Notes

• Behaviour change: a malformed chunk now terminates the stream with an exception instead of being silently skipped. This matches the maintainer intent stated in Raise FerroStreamError in streaming error paths (currently never raised) #16 and the "never silently swallow errors" project convention. Callers relying on silent skipping would need to catch FerroStreamError.