Performance improvements: fix MCP server shutdown and disable caching

- Add proper shutdown handling for MCP servers
  - Listen for stdin EOF (main issue causing 6min delays)
  - Add transport.close() to properly close connections
  - Add 5-minute timeout safety net
  - Handle SIGHUP signal
- Disable Bun caching to avoid timeout errors
- Add Dockerfile.runner for pre-built container option
- Create optimized workflow example without container layer

action.yml

@@ -84,6 +84,7 @@ runs:
       uses: oven-sh/setup-bun@735343b667d3e6f658f44d0eca948eb6282f2b76 # https://github.com/oven-sh/setup-bun/releases/tag/v2.0.2
       with:
         bun-version: 1.2.11
+        cache: false
 
     - name: Install Dependencies
       shell: bash