⚙️ [Maintenance]: Add repository agent onboarding files

[Marius Storhaug (MariusStorhaug)]

This PR splits the agent-onboarding topic out of PSModule/docs PR #61 into the Confluence repository.\n\n## Included\n- Add AGENTS.md\n- Add CLAUDE.md with @AGENTS.md import\n- Add .github/copilot-instructions.md pointing to AGENTS.md\n\n## Why\nEach repository should carry its own onboarding guidance and not rely on org-level fallback files.\n\n## Traceability\n- Related: https://github.com/PSModule/docs/pull/61\n

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^src/	Matches files where path matches this pattern
^README\.md$	Matches files where path matches this pattern

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Super-linter summary

Language	Validation result
CHECKOV	Pass ✅
GITHUB_ACTIONS	Pass ✅
GITLEAKS	Pass ✅
GIT_MERGE_CONFLICT_MARKERS	Pass ✅
MARKDOWN	Fail ❌
NATURAL_LANGUAGE	Pass ✅
POWERSHELL	Pass ✅
PRE_COMMIT	Pass ✅
SPELL_CODESPELL	Pass ✅
TRIVY	Pass ✅
YAML	Pass ✅

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MARKDOWN

/github/workspace/.github/copilot-instructions.md:1 error MD041/first-line-heading/first-line-h1 First line in a file should be a top-level heading [Context: "Follow the instructions in [AG..."]
/github/workspace/CLAUDE.md:1 error MD041/first-line-heading/first-line-h1 First line in a file should be a top-level heading [Context: "@AGENTS.md"]