feat: add process module with arguments and allArguments static methods

- Introduce new 'process' module exposing a Process class with foreign static methods for accessing command-line arguments.
- Implement processSetArguments in main.c to store argc/argv, and processAllArguments in process.c to return them as a Wren list.
- Add --help flag support to CLI, printing usage with optional arguments.
- Include documentation for Process.arguments and Process.allArguments, plus module index and template updates.
- Register process module in modules.c and add Xcode project references for new source files.
- Add test scripts for allArguments and arguments, verifying list type, count, and expected values.

doc/site/modules/process/process.markdown

@@ -0,0 +1,38 @@
+^title Process Class
+
+The Process class lets you work with operating processes, including the
+currently running one.
+
+## Static Methods
+
+### **allArguments**
+
+The list of command-line arguments that were passed when the Wren process was
+spawned. This includes the Wren executable itself, the path to the file being
+run (if any), and any other options passed to Wren itself.
+
+If you run:
+
+    :::bash
+    $ wren file.wren arg
+
+This returns:
+
+    :::wren
+    System.print(Process.allArguments) //> ["wren", "file.wren", "arg"]
+
+### **arguments**
+
+The list of command-line arguments that were passed to your program when the
+Wren process was spawned. This does not include arguments handled by Wren
+itself.
+
+If you run:
+
+    :::bash
+    $ wren file.wren arg
+
+This returns:
+
+    :::wren
+    System.print(Process.arguments) //> ["arg"]