docs: align wire-spec and mark implemented vs proposed

Keep the 45-byte pose frame consistent across docs, simulator, and
prototype, clarify MinIO is not peer sync, and state clearly that the
repo is a from-scratch platform sketch with options rather than mandates.

prototype/src/App.tsx

@@ -268,7 +268,7 @@ export default function App(): JSX.Element {
             {busiest.length === 0 && <div style={styles.dim}>no links in range</div>}
           </Section>
           <Section title="Legend">
-            <div style={styles.dim}>blue line — pose broadcast (5 Hz, ~46 B)</div>
+            <div style={styles.dim}>blue line — pose broadcast (5 Hz, 45 B)</div>
             <div style={styles.dim}>green line — bulk sync (sealed partitions)</div>
             <div style={styles.dim}>flash — broadcast event delivered</div>
             <div style={styles.dim}>red circle — transit object crossing the area</div>