[Phase 2] Generalize cut-release.sh to release non-agent reusables

[github-actions]

Story

As a release engineer,
I want teach cut-release.sh and its tests to cut releases for ci-failure-analyst (and future non-agent reusables),
so that the same audited release primitive cuts tags for every first-party reusable, not just the two agents.

Acceptance Criteria

1. scripts/cut-release.sh ci-failure-analyst 1.0.0 --channel stable --dry-run succeeds (the name is accepted by valid_agent).
2. release_ref/channel_ref emit ci-failure-analyst/v1.0.0 and ci-failure-analyst/stable.
3. tests/test_cut_release.bats covers the new name (valid + dry-run path) and still rejects an unknown name with a non-zero exit.
4. docs/release/versioning.md "What is versioned" table gains a ci-failure-analyst row (reusable workflow + any scripts it carries — currently none beyond the reusable).

Tasks / Subtasks

• Generalize valid_agent() in scripts/cut-release.sh to include ci-failure-analyst (prefer a single source-of-truth list of releasable names). (AC: test issue from agent #1, Go-live improvements for PR review agent #2)
• Verify the error message in the unknown-name branch lists the updated set. (AC: Add @claude delegation, auto-merge, and rebase handling #3)
• Add bats cases: valid ci-failure-analyst dry-run, correct ref names, and unknown-name rejection. (AC: test issue from agent #1, Go-live improvements for PR review agent #2, Add @claude delegation, auto-merge, and rebase handling #3)
• Add the ci-failure-analyst row to the versioning.md table and note it ships only the reusable workflow. (AC: Optimize review: small-PR and incremental fast paths #4)

Dev Notes

• valid_agent() currently hardcodes pr-review | dev-lead (scripts/cut-release.sh). The pure helpers (valid_agent, validate_version, release_ref, channel_ref) are source-guarded so tests/test_cut_release.bats can source the file without running main — preserve that guard.
• Do NOT change --dry-run/--push semantics or remove the immutable-tag overwrite refusal.
• versioning.md currently scopes versioning to dev-lead/pr-review only; generalize the table and prose minimally without contradicting the agent-specific channel docs.
• Testing standard: bats lives under tests/, run with bats tests/test_cut_release.bats; keep cases hermetic (use --dry-run, no real git push).

Project Structure Notes

Edits scripts/cut-release.sh, tests/test_cut_release.bats, docs/release/versioning.md. No new files.

References

• scripts/cut-release.sh#valid_agent
• tests/test_cut_release.bats
• docs/release/versioning.md#what-is-versioned

Likely target surface

• scripts/cut-release.sh
• tests/test_cut_release.bats
• docs/release/versioning.md

Story prepared by the BMAD Scrum Master (Bob) for epic #667. Status: ready-for-dev.