fix(runLink): remove horizontal rule from run link footer

[aaight]

Summary

• Remove the --- markdown horizontal rule from buildRunLink and buildWorkItemRunsLink in src/utils/runLink.ts
• Keep the two leading newlines (\n\n) for spacing above the 🕵️ footer
• Update the unit test regex assertion to match the new format

Trello card: https://trello.com/c/nrJ54yCy/329-remove-horizontal-line-from-run-link-footer-use-empty-line-for-spacing

Changes

• src/utils/runLink.ts — Removed ---\n from both buildRunLink (line 68) and buildWorkItemRunsLink (line 98)
• tests/unit/utils/runLink.test.ts — Updated test description and regex from /^\n\n---\n/ to /^\n\n🕵️/

Test plan

• npx vitest run tests/unit/utils/runLink.test.ts — all 20 tests pass
• npm run lint — no issues
• npm run typecheck — no errors

🤖 Generated with Claude Code

[nhopeatall]

LGTM — Straightforward removal of the --- horizontal rule from both buildRunLink and buildWorkItemRunsLink. The two leading newlines (\n\n) are preserved and continue to provide adequate visual separation in all call sites (PR comments, reviews, progress updates, ack messages). Test regex updated correctly. All CI checks pass.