refactor(root): relocate the contributing guide into .github/ (#63)

refactor(root): relocate the contributing guide into .github/

The estate canonical location is .github/CONTRIBUTING.md, which GitHub
auto-discovers; the root copy is removed and references are updated in
the same
change.

  * .github/CONTRIBUTING.md
      (new)
  * CONTRIBUTING.adoc
      (deleted)
  * MAINTAINERS.adoc
  * ai/0-AI-MANIFEST.a2ml

Author: hyperpolymath

.github/CONTRIBUTING.md

@@ -0,0 +1,21 @@
+# Contributing
+
+Contributions are welcome! Please:
+
+1.  Fork the repository
+
+2.  Create a feature branch from `main`
+
+3.  Ensure all CI checks pass
+
+4.  Submit a pull request
+
+## Standards
+
+This project follows the [Rhodium Standard Repository
+(RSR)](https://github.com/hyperpolymath/standards) conventions.
+
+## License
+
+By contributing, you agree that your contributions will be licensed
+under MPL-2.0 (with MPL-2.0 as automatic legal fallback).

CONTRIBUTING.adoc

@@ -62,4 +62,4 @@ For questions about project governance:
 
 * link:GOVERNANCE.adoc[Governance Model]
 * link:CODE_OF_CONDUCT.md[Code of Conduct]
-* link:CONTRIBUTING.adoc[Contributing Guide]
+* link:.github/CONTRIBUTING.md[Contributing Guide]

MAINTAINERS.adoc

@@ -97,7 +97,7 @@ This repo follows the **Dual-Track** architecture:
 ├── README.adoc                 # High-level pitch — excitement and awe (Rich Human)
 ├── EXPLAINME.adoc              # Developer deep-dive — how it works (Rich Nerd)
 ├── ROADMAP.adoc                # Future direction
-├── CONTRIBUTING.adoc           # Human contribution guide
+├── ../.github/CONTRIBUTING.md           # Human contribution guide
 ├── GOVERNANCE.adoc             # Decision-making model
 ├── Justfile                    # Task runner
 ├── Containerfile               # OCI build