feat: implement interactive REPL with line editing and syntax highlighting in Wren

Replace the simple fgets-based REPL loop with a full-featured interactive Wren REPL module. The new implementation supports cursor movement via arrow keys, Ctrl-A/E for line start/end, Ctrl-C/D for exit/delete, character insertion/deletion, and syntax highlighting of the current input line. The C side now imports the "repl" Wren module and runs the libuv event loop instead of blocking on stdin reads.

src/cli/modules.c

@@ -5,6 +5,7 @@
 
 #include "io.wren.inc"
 #include "os.wren.inc"
+#include "repl.wren.inc"
 #include "scheduler.wren.inc"
 #include "timer.wren.inc"
 
@@ -162,6 +163,8 @@ static ModuleRegistry modules[] =
       STATIC_METHOD("allArguments", processAllArguments)
     END_CLASS
   END_MODULE
+  MODULE(repl)
+  END_MODULE
   MODULE(scheduler)
     CLASS(Scheduler)
       STATIC_METHOD("captureMethods_()", schedulerCaptureMethods)

src/cli/vm.c

@@ -6,8 +6,6 @@
 #include "scheduler.h"
 #include "vm.h"
 
-#define MAX_LINE_LENGTH 1024 // TODO: Something less arbitrary.
-
 // The single VM instance that the CLI uses.
 static WrenVM* vm;
 
@@ -259,23 +257,9 @@ int runRepl()
   printf("\\\\/\"-\n");
   printf(" \\_/   wren v%s\n", WREN_VERSION_STRING);
 
-  char line[MAX_LINE_LENGTH];
-
-  for (;;)
-  {
-    printf("> ");
-
-    if (!fgets(line, MAX_LINE_LENGTH, stdin))
-    {
-      printf("\n");
-      break;
-    }
-
-    // TODO: Handle failure.
-    wrenInterpret(vm, line);
-
-    // TODO: Automatically print the result of expressions.
-  }
+  wrenInterpret(vm, "import \"repl\"\n");
+  
+  uv_run(loop, UV_RUN_DEFAULT);
 
   freeVM();