[Phase 3] Repin ci-failure-analyst caller, template, and docs to the channel tag

[github-actions]

Story

As a maintainer,
I want repin all three ci-failure-analyst pin sites to @ci-failure-analyst/stable,
so that the reusable is pinned to a protected, accurate channel tag — matching the dev-lead/pr-review standard — and the off-main SHA is gone for good.

Acceptance Criteria

1. .github/workflows/ci-failure-analyst.lock.yml, templates/ci-failure-analyst.yml, and docs/aw/ci-failure-analyst.md pin …/ci-failure-analyst-reusable.yml@ci-failure-analyst/stable (no 40-hex SHA, no # main).
2. The stopgap on-main SHA pin (from story id 2) is fully removed from all three sites.
3. The ci-failure-analyst workflow still triggers on check_run: completed failures and posts its diagnostic comment — no behavior change beyond the ref.

Tasks / Subtasks

• Replace the uses: ref in the lock stub and template with @ci-failure-analyst/stable. (AC: test issue from agent #1, Go-live improvements for PR review agent #2)
• Update the pin shown in the docs/aw/ci-failure-analyst.md architecture diagram to the channel tag. (AC: test issue from agent #1, Go-live improvements for PR review agent #2)
• Confirm the three refs match the dev-lead/pr-review caller form exactly. (AC: test issue from agent #1, Add @claude delegation, auto-merge, and rebase handling #3)

Dev Notes

• Requires the channel tag to exist — gated on story id 5; and ordered after the stopgap (story id 2) which it supersedes.
• Mirror the exact caller form already used by dev-lead.yml (@dev-lead/stable) and pr-review-trigger.yml (@pr-review/stable).
• Only the uses: ref (and the doc mirror at docs/aw/ci-failure-analyst.md:25) change; leave triggers, permissions, concurrency, and job if: guards untouched.

Project Structure Notes

Edits the existing lock stub, template, and doc; no new files.

References

• .github/workflows/ci-failure-analyst.lock.yml#L33
• templates/ci-failure-analyst.yml#L44
• docs/aw/ci-failure-analyst.md#L25
• .github/workflows/dev-lead.yml#L51

Likely target surface

• .github/workflows/ci-failure-analyst.lock.yml
• templates/ci-failure-analyst.yml
• docs/aw/ci-failure-analyst.md

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