docs: add Setup wiki page

Setup.md

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+# Setup
+
+## Purpose
+
+Hardware/firmware project. Keep setup, flashing notes, target boards, binary provenance, and lab safety boundaries explicit.
+
+## Local Requirements
+
+Document runtime, toolchain, hardware, environment variables, and dependency setup here.
+
+## First Run
+
+Add the smallest known-good setup path. Keep secrets in local environment files that are ignored by Git.