feat: add networking module with TCP Socket/Server and example applications

Implement a full-featured `net` module supporting TCP `Socket` and `Server` classes via libuv, including example applications (chat server, echo server, HTTP client/server, file explorer, system dashboard) and benchmark scripts (fibonacci, n-body). Add GEMINI.md project documentation and Stderr class to io module.

test_suspend.wren

@@ -0,0 +1,10 @@
+System.print("Start")
+Fiber.new {
+  System.print("In new fiber, suspending")
+  Fiber.suspend()
+  System.print("New fiber resumed")
+}.call()
+
+System.print("Back in main fiber")
+Fiber.suspend()
+System.print("Main fiber resumed")