Refresh HANDOFF workflow counts and self-test docs

[ArchonVII]

Summary

Refresh stale github-workflows docs after PR #35's accounting identified workflow-count drift and missing documentation around self-test/actionlint caller coverage.

Acceptance Criteria

• HANDOFF.md no longer says both 14 and 15 reusable workflows when the repo has 17 reusable workflows plus non-reusable self-test.yml.
• README or HANDOFF documents self-test.yml as this repo's own direct-trigger test workflow.
• README or examples docs clarify whether actionlint.yml should have an example caller or why it intentionally does not.
• No workflow behavior changes are included unless separately scoped.

Related

• docs(workflow): add release workflow breakdown #35
• docs(ecosystem): refresh snapshot status archon-setup#63