docs: add maintainer ownership policy

[DeusData]

Summary

• Add .github/CODEOWNERS with @DeusData as the binding owner for all paths.
• Add MAINTAINERS.md as the advisory delegation map for future co-maintainers.
• Split review areas by the actual repository layout: MCP, CLI/install, pipeline, language extraction/LSP, store/query, foundation/runtime, graph UI, tests/repro, packaging, security, CI/release, and governance.
• Document stricter operational authority for dry runs, release workflow dispatch, package publishing, security advisories, workflow/ruleset changes, and branch protection.

Notes

• This repo is user-owned, so the policy uses individual handles rather than GitHub teams.
• Delegated reviewers belong in MAINTAINERS.md first. They should only be added to CODEOWNERS once they are allowed to satisfy the binding code-owner approval gate.
• CI run authority is documented here, but actual enforcement still depends on GitHub collaborator permissions, branch protection/rulesets, and protected environments for release jobs.

Tests

• PASS: CODEOWNERS line-shape validation with awk
• PASS: git diff --check -- .github/CODEOWNERS MAINTAINERS.md