ci: adopt the organization commit-lint caller

[ss-o]

Summary

• Adds .github/workflows/commit-lint.yml, a thin caller for the organization commit-lint suite in z-shell/.github (Conventional Commit messages and PR title, banned bot/AI-agent Co-authored-by trailers, branch-name shape, ADR-0022 issue link).
• Pinned to z-shell/.github main at 6ab97b2, with permissions: contents: read on both the workflow and the job (fix(ci): Lint Commits fails at startup so commit policy is unenforced .github#575).

Verification

• actionlint .github/workflows/commit-lint.yml is clean.
• The commit carries no trailer, and this PR is its own first run of the caller.

Agent handoff

No handoff needed.

Closes #227

[cloudflare-workers-and-pages]

Deploying src with    Cloudflare Pages

Latest commit:	93a6f32
Status:	✅  Deploy successful!
Preview URL:	https://50bc4a18.zi-src.pages.dev
Branch Preview URL:	https://feature-227-commit-lint.zi-src.pages.dev

View logs

[ss-o]

Agent handoff

• State: blocked on the Copilot review quota (ADR-0026, decision 3). This is a class 1 repository, so the fallback review does not apply.
• Evidence: on 2026-09-26, POST requested_reviewers for copilot-pull-request-reviewer[bot] returned 201 for head 93a6f32c, but no review_requested timeline event followed and no review ran.
• Next: request the Copilot review again once the allowance resets, act on any threads, then squash-merge. Every required check already passes on this head.