fix(docs): repair the contributing guide content defects

Mechanical repairs to the guide, each anchored on a known-broken form:

- unescaped \# -> #
- rebuilt the hard-wrapped setup block into one command per line
- replaced invalid `():` commit header
- dedented headings that rendered as code

No prose is rewritten; only the broken forms are corrected.

Author: hyperpolymath

.github/CONTRIBUTING.md

@@ -1,44 +1,44 @@
 # Clone the repository
 
-git clone <https://github.com/hyperpolymath/developer-ecosystem.git> cd
-developer-ecosystem
+git clone https://github.com/hyperpolymath/developer-ecosystem.git
+cd developer-ecosystem
 
-# Using Nix (recommended for reproducibility)
+# Using Guix (recommended for reproducibility)
 
-nix develop
+guix develop
 
 # Or using toolbox/distrobox
 
-toolbox create developer-ecosystem-dev toolbox enter
-developer-ecosystem-dev \# Install dependencies manually
+toolbox create developer-ecosystem-dev
+toolbox enter developer-ecosystem-dev
+# Install dependencies manually
 
 # Verify setup
 
-just check \# or: cargo check / mix compile / etc. just test \# Run test
-suite
+just check   # or: cargo check / mix compile / etc.
+just test    # Run test suite
 
+### Repository Structure
 
-    ### Repository Structure
-
-developer-ecosystem/ ├── 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) │ ├──
+developer-ecosystem/ ├── 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.nix \# Nix
-flake (Perimeter 1) └── Justfile \# Task runner (Perimeter 1)
+├── CONTRIBUTING.md # This file ├── GOVERNANCE.md ├── LICENSE ├──
+MAINTAINERS.md ├── README.adoc ├── SECURITY.md ├── flake.nix # Nix
+flake (Perimeter 1) └── Justfile # Task runner (Perimeter 1)
 
 
     ---
 
-    ## How to Contribute
+## How to Contribute
 
-    ### Reporting Bugs
+### Reporting Bugs
 
     **Before reporting**:
     1. Search existing issues
@@ -55,7 +55,7 @@ flake (Perimeter 1) └── Justfile \# Task runner (Perimeter 1)
     - Expected vs actual behaviour
     - Logs, screenshots, or minimal reproduction
 
-    ### Suggesting Features
+### Suggesting Features
 
     **Before suggesting**:
     1. Check the [roadmap](ROADMAP.md) if available
@@ -71,7 +71,7 @@ flake (Perimeter 1) └── Justfile \# Task runner (Perimeter 1)
     - Alternatives considered
     - Which perimeter this affects
 
-    ### Your First Contribution
+### Your First Contribution
 
     Look for issues labelled:
 
@@ -82,22 +82,25 @@ flake (Perimeter 1) └── Justfile \# Task runner (Perimeter 1)
 
     ---
 
-    ## Development Workflow
+## Development Workflow
 
-    ### Branch Naming
+### 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)
+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
+### Commit Messages
 
     We follow [Conventional Commits](https://www.conventionalcommits.org/):
 
-():
+type(scope): description
+
+Body: what changed and why.
 
+Footer: issue reference, e.g. Closes #123
 \[optional body\]
 
 \[optional footer\]