Detailed wiki content repair: Setup

Setup.md

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+# Setup
+
+## Proven Setup Signals
+
+| Signal | Detail |
+|---|---|
+| Arduino sketches | handshake-capture-c6/handshake-capture-c6.ino |
+| README files | README.md, handshake-capture-c6/README.md |
+
+## Setup Path
+
+- Open Arduino sketches only after confirming board package, library dependencies, and target board.
+
+## Environment Rules
+
+- Keep local secrets out of Git.
+- Put generated build output outside source control.
+- Prefer a clean checkout when validating setup instructions.
+- Record the exact command that works in the readiness issue before closing it.
+
+## Current Gaps
+
+- No setup gaps were inferred from inspected evidence.