fix(docs): rebuild the mangled repository-structure tree

The tree block was hard-wrapped by the AsciiDoc->Markdown conversion, so it
rendered as a paragraph rather than a tree, and it still listed CONTRIBUTING.md
at the repository root, where the guide no longer lives.

Rebuilt from the tree's own content: depth recovered from the `|` continuation
bars that survived the wrap, the guide entry moved under `.github/`, `#` escapes
unescaped, the last entry of each group restored to `└──`, and the block fenced
so it renders as a tree. Every annotation ("Perimeter 1-2") is preserved -
nothing is invented and nothing is dropped.

Author: hyperpolymath

.github/CONTRIBUTING.md

@@ -16,38 +16,39 @@ just test    # Run test suite
 ```
 
 ### Repository Structure
-```
+
+```text
 halideiser/
-├── 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)
-├── .machine_readable/   # ALL machine-readable content (Perimeter 1)
-│   ├── *.a2ml           # State files (STATE, META, ECOSYSTEM, etc.)
-│   ├── bot_directives/  # Bot configs
-│   └── contractiles/    # Policy contracts (k9, dust, lust, must, trust)
-├── .well-known/         # Protocol files (Perimeter 1-3)
-├── .github/             # GitHub config (Perimeter 1)
+├── 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)
+├── .machine_readable/ # ALL machine-readable content (Perimeter 1)
+│   ├── *.a2ml # State files (STATE, META, ECOSYSTEM, etc.)
+│   ├── bot_directives/ # Bot configs
+│   └── contractiles/ # Policy contracts (k9, dust, lust, must, trust)
+├── .well-known/ # Protocol files (Perimeter 1-3)
+├── .github/ # GitHub config (Perimeter 1)
+│   ├── CONTRIBUTING.md # This file
 │   ├── 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 — fallback (Perimeter 1)
-├── guix.scm             # Guix package — primary (Perimeter 1)
-└── Justfile             # Task runner (Perimeter 1)
+├── flake.nix # Nix flake — fallback (Perimeter 1)
+├── guix.scm # Guix package — primary (Perimeter 1)
+└── Justfile # Task runner (Perimeter 1) ```
 ```
 
 ---