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

@@ -35,30 +35,30 @@ Tested on OCaml 4.14.2 (the constraint in `dune-project` is `>=`
 
 ### Repository Structure
 
-    affinescript/
-    ├── lib/                 # Compiler core (lexer, parser, typechecker, codegen, verifier)
-    ├── bin/                 # CLI driver — `_build/default/bin/main.exe`
-    ├── stdlib/              # Standard library `.affine` modules
-    ├── test/                # Alcotest suites (lexer, golden, e2e fixtures)
-    ├── tests/               # Topic-grouped tests (borrow, codegen, effects, parser, …)
-    ├── examples/            # Self-contained example programs
-    ├── conformance/         # Conformance test corpus
-    ├── docs/                # Specs, decisions, guides
-    ├── packages/            # Aggregate JS/TS/ binding packages
-    ├── editors/             # Editor integrations
-    ├── js/                  # `js_of_ocaml` playground (built into `playground.bc.js`)
-    ├── .machine_readable/   # Machine-readable metadata (`.a2ml`) — see 0-AI-MANIFEST.a2ml
-    ├── .github/             # CI workflows, issue templates
-    ├── CODE_OF_CONDUCT.md
-    ├── CONTRIBUTING.md      # This file
-    ├── LICENSE / LICENSES   # MIT OR AGPL-3.0-or-later
-    ├── MAINTAINERS.adoc
-    ├── README.adoc
-    ├── SECURITY.md
-    ├── dune-project
-    └── justfile
-
-’’’’’
+```text
+affinescript/
+├── lib/ # Compiler core (lexer, parser, typechecker, codegen, verifier)
+├── bin/ # CLI driver — `_build/default/bin/main.exe`
+├── stdlib/ # Standard library `.affine` modules
+├── test/ # Alcotest suites (lexer, golden, e2e fixtures)
+├── tests/ # Topic-grouped tests (borrow, codegen, effects, parser, …)
+├── examples/ # Self-contained example programs
+├── conformance/ # Conformance test corpus
+├── docs/ # Specs, decisions, guides
+├── packages/ # Aggregate JS/TS/ binding packages
+├── editors/ # Editor integrations
+├── js/ # `js_of_ocaml` playground (built into `playground.bc.js`)
+├── .machine_readable/ # Machine-readable metadata (`.a2ml`) — see 0-AI-MANIFEST.a2ml
+├── .github/ # CI workflows, issue templates
+│   └── CONTRIBUTING.md # This file
+├── CODE_OF_CONDUCT.md
+├── LICENSE / LICENSES # MIT OR AGPL-3.0-or-later
+├── MAINTAINERS.adoc
+├── README.adoc
+├── SECURITY.md
+├── dune-project
+└── justfile ’’’’’
+```
 
 ## How to Contribute