spec: TOC sub-items for 3.5 and 4.5

Made-with: Cursor

Author: alpha912

SPECIFICATION.md

@@ -14,9 +14,9 @@
 1. [Introduction](#1-introduction)
 2. [Terminology](#2-terminology)
 3. [Protocol Overview](#3-protocol-overview)
-3.5. [Minimal Interop Flow v0.2.0](#35-minimal-interop-flow-v020)
+   - [3.5. Minimal Interop Flow v0.2.0](#35-minimal-interop-flow-v020)
 4. [MaterialDNA Specification](#4-materialdna-specification)
-4.5. [ProductDNA Specification](#45-productdna-specification)
+   - [4.5. ProductDNA Specification](#45-productdna-specification)
 5. [LoopCoin Specification](#5-loopcoin-specification)
 6. [LoopSignal Specification](#6-loopsignal-specification)
 7. [LoopCost Calculation](#7-loopcost-calculation)