Fix agent onboarding doc gaps: missing CONTRIBUTING.md, broken link, missing examples

[Marius Storhaug (MariusStorhaug)]

Why

Small gaps found while researching AGENTS.md routing guidance for PSModule module repositories:

1. AGENTS.md (and its counterpart in MSXOrg/docs) links to CONTRIBUTING.md, which didn't exist in this repo.
2. Modules/Repository-Defaults.md had a broken relative link to ../../Ways-of-Working/Git-Worktrees.md — that page actually lives in MSXOrg/docs.
3. The "Agent onboarding files" section described the AGENTS.md/CLAUDE.md/copilot-instructions.md pattern only in prose, with no copy-pasteable example — unlike the README section in the same file, which has full examples.

What changed

• Added CONTRIBUTING.md at repo root: layout, contribution workflow (worktree/branch, draft PR, micro-commits), local build/preview (zensical build --clean), and linting (super-linter), all confirmed against .github/workflows/Docs.yml.
• Fixed the broken relative link in Repository-Defaults.md to point to the canonical https://msxorg.github.io/docs/Ways-of-Working/Git-Worktrees/.
• Added fenced-code examples for AGENTS.md, CLAUDE.md, and .github/copilot-instructions.md to the "Agent onboarding files" section, so module repositories (e.g. Template-PSModule) have something to copy directly.

Docs-only change; no build/test tooling changes needed.

[github-actions]

Super-linter summary

Language	Validation result
CHECKOV	Pass ✅
GITHUB_ACTIONS	Pass ✅
GITHUB_ACTIONS_ZIZMOR	Pass ✅
GITLEAKS	Pass ✅
GIT_MERGE_CONFLICT_MARKERS	Pass ✅
HTML	Pass ✅
JAVASCRIPT_ES	Pass ✅
JAVASCRIPT_PRETTIER	Pass ✅
MARKDOWN	Pass ✅
NATURAL_LANGUAGE	Pass ✅
POWERSHELL	Pass ✅
PRE_COMMIT	Pass ✅
SPELL_CODESPELL	Pass ✅
TRIVY	Pass ✅
YAML	Pass ✅

All files and directories linted successfully

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[Marius Storhaug (MariusStorhaug)]

Superseded by #79 and #82, which independently merged to main and cover the same three gaps (CONTRIBUTING.md, broken Ways-of-Working link, agent onboarding examples) — using a cleaner approach (pointing to Template-PSModule as the live example instead of inline snippets). Closing as redundant; no unique changes remain in this branch.