feat(prototype): 2D swarm data-plane visualization

Top-down SVG view: patrol flight with separation and obstacle avoidance,
mesh links appearing within radio range, pose-broadcast flashes, bulk
sync transfers with live rate and cumulative up/down counters, channel
hopping and battery per drone. Pure client-side simulation (Vite/React/TS).

prototype/README.md

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+# Swarm visualization prototype
+
+A 2D top-down view of the swarm data plane from [04 — Swarm sync](../docs/04-swarm-sync.md): drones patrol an area with static and mobile obstacles, exchange 5 Hz pose broadcasts (blue link flashes), and run opportunistic bulk sync of sealed partitions (green links with live rate and cumulative up/down counters).
+
+No backend — a pure client-side simulation of the same behavioral model the Python simulator implements over real Parquet and UDP.
+
+## Run
+
+```bash
+npm install
+npm run dev     # http://localhost:5173
+```
+
+## What to look at
+
+- **Links appear and disappear** as drones move in and out of radio range; persistent links render semi-transparent, broadcast deliveries flash them briefly.
+- **Busy links turn green** and show current rate plus total transferred (`↑` / `↓`) — the bandwidth budget from the sync design made visible.
+- **Per-drone label**: id, current Wi-Fi channel (hopping), battery.
+- Controls: drone count, simulation speed, pause.