Fix/contributing guide structure tree (#66)

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- [ ] Tests pass (`just test` or equivalent)
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- [ ] `.machine_readable/STATE.a2ml` updated (if project state changed)
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- [ ] Documentation updated for user-facing changes
- [ ] `TOPOLOGY.md` updated (if architecture changed)
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---------

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

Author: hyperpolymath

.github/CONTRIBUTING.md

@@ -47,7 +47,7 @@ dictask/
 ├── SECURITY.md
 ├── flake.guix            # Guix flake — fallback (Perimeter 1)
 ├── guix.scm             # Guix package — primary (Perimeter 1)
-└── Justfile             # Task runner (Perimeter 1)
+└── Justfile             # Task runner
 ```
 
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