feat(plugin/ruview): wire @ruvnet/rvagent MCP server (plugin v0.3.0)

Registers @ruvnet/rvagent 0.1.0 as an MCP server in plugin.json, so
installing the ruview plugin auto-exposes bfld_last_scan, bfld_subscribe,
presence_now, vitals_get_breathing, vitals_get_heart_rate, vitals_get_all,
and vitals_fetch as first-class Claude Code tool calls instead of shell-out
via the ruview-rvagent skill.

Updates the ruview-rvagent skill + Codex prompt with a Quickstart section
covering the published npm package and the RVAGENT_SENSING_URL override.
The existing Rust-crate exploration content (vendor/ruvector/crates/rvAgent)
remains as the substrate for deeper RVF-aware agentic flows.

Co-Authored-By: claude-flow <ruv@ruv.net>

plugins/ruview/.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "ruview",
   "description": "End-to-end RuView (WiFi-DensePose) toolkit for Claude Code: onboarding, ESP32 hardware setup, configuration, sensing applications, model training, advanced multistatic sensing, witness verification, BFLD privacy layer, and rvAgent + RVF agentic flows — from practical to advanced.",
-  "version": "0.2.0",
+  "version": "0.3.0",
   "author": {
     "name": "ruvnet",
     "url": "https://github.com/ruvnet/RuView"
@@ -19,5 +19,14 @@
     "edge-ai",
     "model-training",
     "onboarding"
-  ]
+  ],
+  "mcpServers": {
+    "rvagent": {
+      "command": "npx",
+      "args": ["-y", "@ruvnet/rvagent"],
+      "env": {
+        "RVAGENT_SENSING_URL": "http://localhost:3000"
+      }
+    }
+  }
 }