docs: close issues #17–#20 (matrix, story, examples, adopters)

[cobusgreyling]

Summary

Implements all four good-first-issue backlog items:

• docs: add Cursor and Windsurf rows to primitives-matrix.md #17 — Cursor + Windsurf columns in docs/primitives-matrix.md (scheduling, skills, sub-agents, appendix transfer recipes)
• story: production write-up for Post-Merge Cleanup pattern #18 — Production Post-Merge Cleanup story with explicit failures, surprises, and metrics
• examples: add issue-triage examples for Grok, Claude Code, and Codex #19 — Issue Triage examples for Grok, Claude Code, and Codex (L1 propose-only week one)
• docs: add your loop to adopters.md #20 — Maintainer loop rows in docs/adopters.md

Also updates examples/README.md, examples/grok/README.md, and stories/README.md cross-links.

Closes #17, #18, #19, #20

[github-actions]

Loop Readiness Audit

Score: 100/100 (L3)

Strong loop readiness — good candidate for L3 with explicit gates.

No suggestions — looking good.

_{Posted by audit.yml · loop-audit docs}