Realign with template: restore Copilot runbook and review-loop sections, add markdownlint, fix .editorconfig, rename rulesets

[ptr727]

Drift found while auditing derived repos against ptr727/ProjectTemplate, per the verbatim-carry contract (introduced in ptr727/ProjectTemplate#124):

• .github/copilot-instructions.md is truncated - it lacks the "GitHub Copilot Review Runbook" (the GraphQL requestReviews mechanics, login note, retry/resolve patterns). Restore it verbatim from the template (adapt <owner>/<repo>).
• AGENTS.md lacks the "PR Review Etiquette" / "Expected Review Loop" sections - carry the contract verbatim.
• Missing .markdownlint-cli2.jsonc. Copy the template's .markdownlint-cli2.jsonc verbatim.
• .editorconfig line-ending drift - end_of_line = crlf only under [*.md]; carry the template's full per-extension rules (copy the template's .editorconfig verbatim). .gitattributes is correct.
• Ruleset names Develop branch/Main branch - the template requires exact lowercase develop/main (load-bearing). Recreate via the README JSON export/import.

App-token client-id and signed-commit rulesets are already correct. The absence of .devcontainer/ is likely intentional (this is a Docker-image repo, not the .NET/Python library template) - not flagged.