refactor(root): relocate the contributing guide into .github/ (#59)

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)

Author: hyperpolymath

.github/CONTRIBUTING.md

@@ -0,0 +1,103 @@
+# Clone the repository
+
+git clone <https://github.com/hyperpolymath/nextgen-languages.git> cd
+nextgen-languages
+
+# Using Guix (recommended for reproducibility)
+
+guix develop
+
+# Or using toolbox/distrobox
+
+toolbox create nextgen-languages-dev toolbox enter nextgen-languages-dev
+\# Install dependencies manually
+
+# Verify setup
+
+just check \# or: cargo check / mix compile / etc. just test \# Run test
+suite
+
+
+    ### Repository Structure
+
+nextgen-languages/ ├── src/ \# Source code (Perimeter 1-2) ├── lib/ \#
+Library code (Perimeter 1-2) ├── extensions/ \# Extensions (Perimeter 2)
+├── plugins/ \# Plugins (Perimeter 2) ├── tools/ \# Tooling (Perimeter
+2) ├── docs/ \# Documentation (Perimeter 3) │ ├── architecture/ \# ADRs,
+specs (Perimeter 2) │ └── proposals/ \# RFCs (Perimeter 3) ├── examples/
+\# Examples (Perimeter 3) ├── spec/ \# Spec tests (Perimeter 3) ├──
+tests/ \# Test suite (Perimeter 2-3) ├── .well-known/ \# Protocol files
+(Perimeter 1-3) ├── .github/ \# GitHub config (Perimeter 1) │ ├──
+ISSUE_TEMPLATE/ │ └── workflows/ ├── CHANGELOG.md ├── CODE_OF_CONDUCT.md
+├── CONTRIBUTING.md \# This file ├── GOVERNANCE.md ├── LICENSE ├──
+MAINTAINERS.md ├── README.adoc ├── SECURITY.md ├── flake.guix \# Guix
+flake (Perimeter 1) └── Justfile \# Task runner (Perimeter 1)
+
+
+    ---
+
+    ## 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/nextgen-languages/labels/good%20first%20issue) — Simple Perimeter 3 tasks
+    - [`help wanted`](https://github.com/hyperpolymath/nextgen-languages/labels/help%20wanted) — Community help needed
+    - [`documentation`](https://github.com/hyperpolymath/nextgen-languages/labels/documentation) — Docs improvements
+    - [`perimeter-3`](https://github.com/hyperpolymath/nextgen-languages/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/):
+
+():
+
+\[optional body\]
+
+\[optional footer\]