feat: Phase 9 Serial MCP server + app icon & version title (v0.2.0)

Phase 9 (AI integration) complete -- AI agents can send/receive serial
while the user watches live in the GUI, with the GUI as sole COM-port owner.

- ETTerms.SerialMcp: stdio MCP server (net8.0 + ModelContextProtocol SDK)
  exposing serial_list / serial_attach / serial_write / serial_read
  (waitFor + timeoutMs) / serial_detach; forwards over named pipe.
- GUI SerialBridgeServer (pipe etterms-serial) + SerialBridge endpoint;
  SessionPage.WriteFromAi echoes MCP-sourced TX tagged [AI] (magenta).
- App icon: window title bar / taskbar / exe now use Choco_256x256.ico
  (embedded via AppAssets); title bar shows ETTerms Version vX.Y.Z.
- About page: large Choco icon (Zoom, no crop).
- Docs: ARCHITECTURE.md + CLAUDE.md mark Phase 9 done; docs/serial-mcp-guide.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ETTerms.slnx

@@ -1,5 +1,6 @@
 <Solution>
   <Folder Name="/src/">
     <Project Path="src/ETTerms/ETTerms.csproj" />
+    <Project Path="src/ETTerms.SerialMcp/ETTerms.SerialMcp.csproj" />
   </Folder>
 </Solution>