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

.github/CONTRIBUTING.md

@@ -0,0 +1,128 @@
+# Contributing to Phronesis
+
+Thanks for your interest in contributing! Phronesis is a neuro-symbolic
+policy language for provably-safe agentic ethical reasoning, with an
+Elixir/BEAM reference implementation and a Rust → WASM production
+compiler.
+
+## Getting Started
+
+``` bash
+# Clone the repository
+git clone https://github.com/hyperpolymath/phronesis.git
+cd phronesis
+
+# Install dependencies (BEAM toolchain + just)
+mix deps.get
+
+# Verify setup
+just build   # mix compile
+just test    # run the test suite
+```
+
+### Repository Structure
+
+    phronesis/
+    ├── lib/phronesis/        # Reference implementation (Elixir/BEAM):
+    │                         #   lexer, parser, type checker, interpreter,
+    │                         #   consensus, LSP, debugger, profiler, reflexion
+    ├── compiler/             # Rust → WASM compiler (phronesis-ast, phronesis-wasm)
+    ├── spec/                 # Grammar (EBNF) + formal semantics
+    ├── formal/               # TLA+ consensus specification
+    ├── academic/             # Formal proofs (Lean4 / Agda / Coq)
+    ├── conformance/          # Conformance test suites
+    ├── bench/                # Benchmarks
+    ├── docs/                 # AsciiDoc design docs (incl. REFLEXION.adoc)
+    ├── examples/             # Example .phr policies
+    ├── test/                 # ExUnit test suite
+    ├── editors/              # VSCode extension + grammars
+    ├── .machine_readable/    # A2ML metadata + contractiles
+    ├── .github/workflows/    # CI/CD
+    ├── CHANGELOG.md  CODE_OF_CONDUCT.md  CONTRIBUTING.md  SECURITY.md
+    ├── GOVERNANCE.adoc  MAINTAINERS.adoc  README.adoc  EXPLAINME.adoc
+    ├── LICENSE  LICENSES/    # MPL-2.0 (code) + CC-BY-SA-4.0 (docs)
+    ├── mix.exs  Justfile  Mustfile
+    └── guix.scm
+
+’’’’’
+
+## How to Contribute
+
+### Reporting Bugs
+
+**Before reporting**: 1. Search existing issues 2. Check if it’s already
+fixed in `main` 3. Determine which perimeter the bug affects
+
+**When reporting**:
+
+Use the [bug report template](.github/ISSUE_TEMPLATE/bug_report.md) and
+include:
+
+- Clear, descriptive title
+
+- Environment details (OS, versions, toolchain)
+
+- Steps to reproduce
+
+- Expected vs actual behaviour
+
+- Logs, screenshots, or minimal reproduction
+
+### Suggesting Features
+
+**Before suggesting**: 1. Check the [roadmap](ROADMAP.md) if available
+2. Search existing issues and discussions 3. Consider which perimeter
+the feature belongs to
+
+**When suggesting**:
+
+Use the [feature request
+template](.github/ISSUE_TEMPLATE/feature_request.md) and include:
+
+- Problem statement (what pain point does this solve?)
+
+- Proposed solution
+
+- Alternatives considered
+
+- Which perimeter this affects
+
+### Your First Contribution
+
+Look for issues labelled:
+
+- [`good` `first`
+  `issue`](https://github.com/hyperpolymath/phronesis/labels/good%20first%20issue)
+  — Simple Perimeter 3 tasks
+
+- [`help`
+  `wanted`](https://github.com/hyperpolymath/phronesis/labels/help%20wanted)
+  — Community help needed
+
+- [`documentation`](https://github.com/hyperpolymath/phronesis/labels/documentation)
+  — Docs improvements
+
+- [`perimeter-3`](https://github.com/hyperpolymath/phronesis/labels/perimeter-3)
+  — Community sandbox scope
+
+’’’’’
+
+## Development Workflow
+
+### Branch Naming
+
+    docs/short-description       # Documentation (P3)
+    test/what-added              # Test additions (P3)
+    feat/short-description       # New features (P2)
+    fix/issue-number-description # Bug fixes (P2)
+    refactor/what-changed        # Code improvements (P2)
+    security/what-fixed          # Security fixes (P1-2)
+
+### Commit Messages
+
+We follow [Conventional Commits](https://www.conventionalcommits.org/):
+\`\`\` ():
+
+\[optional body\]
+
+\[optional footer\]