chore: rename project to excalidraw-mcp-sentinel

- Package name: @sanjibdevnath/mcp-excalidraw-local → excalidraw-mcp-sentinel
- GitHub repo: celstnblacc/mcp-excalidraw-local → celstnblacc/excalidraw-mcp-sentinel
- Docker images, CLI binary, CI workflows, docs all updated
- Version reset to 1.0.0 for independent release track
- Added "Why this fork?" section to README
- Removed superseded planning docs (PLAN.md, PLAN_v2.md, REVIEW.md, HANDOFF.md)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

claude_desktop_config.json

@@ -2,7 +2,7 @@
   "mcpServers": {
     "excalidraw-canvas": {
       "command": "node",
-      "args": ["/absolute/path/to/mcp-excalidraw-local/dist/index.js"],
+      "args": ["/absolute/path/to/excalidraw-mcp-sentinel/dist/index.js"],
       "env": {
         "CANVAS_PORT": "3000"
       }