Scaffold repo: docs layout, guidelines and initial plan

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013kj58Jugkic783b8ZrtTVZ

docs/GUIDELINES.md

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+---
+type: default
+---
+# Display client guidelines
+
+## 1. The client knows the contract, not the car
+- No CAN frame IDs, no DBC knowledge, no device paths. Topic names and payload
+  schemas only.  
+- If rendering something requires new knowledge of the vehicle, that knowledge
+  belongs upstream in the decoder, not here.
+
+## 2. Render whatever state exists, immediately
+- Retained topics mean a client connecting mid-drive has state at once. Never
+  block the first paint on a full set of signals.  
+- Missing is a normal state and must have a visual form. It is not an error.
+
+## 3. Design for a split screen
+- The screen may be shared with another app. Do not assume full width.
+
+## 4. To be added