feat: implement MCP HTTP server endpoint with authentication (#18670)

# Add MCP HTTP server with streamable transport support

- Add MCP HTTP server with streamable transport support
- Integrate with existing toolsdk for Coder workspace operations
- Add comprehensive E2E tests with OAuth2 bearer token support
- Register MCP endpoint at /api/experimental/mcp/http with authentication
- Support RFC 6750 Bearer token authentication for MCP clients

Change-Id: Ib9024569ae452729908797c42155006aa04330af
Signed-off-by: Thomas Kosiewski <tk@coder.com>

coderd/coderd.go

@@ -972,6 +972,10 @@ func New(options *Options) *API {
 		r.Route("/aitasks", func(r chi.Router) {
 			r.Get("/prompts", api.aiTasksPrompts)
 		})
+		r.Route("/mcp", func(r chi.Router) {
+			// MCP HTTP transport endpoint with mandatory authentication
+			r.Mount("/http", api.mcpHTTPHandler())
+		})
 	})
 
 	r.Route("/api/v2", func(r chi.Router) {