feat: rename process module to os and add Platform class with name and isPosix methods

Rename the "process" module to "os" across all source files, documentation, tests, and build configuration. Add a new Platform class to the os module with static methods `name` (returns OS string like "Windows", "Linux", "OS X", "iOS", "Unix", "POSIX", or "Unknown") and `isPosix` (returns bool indicating POSIX compliance). Update all import paths from "process" to "os" in test files and module registrations. Move process.c/h to os.c/h, rename processSetArguments to osSetArguments, and regenerate the os.wren.inc bytecode source. Add documentation pages for the os module and Platform class.

doc/site/modules/template.html

@@ -37,7 +37,7 @@
       <h2>cli</h2>
       <ul>
         <li><a href="io">io</a></li>
-        <li><a href="process">process</a></li>
+        <li><a href="os">os</a></li>
         <li><a href="scheduler">scheduler</a></li>
         <li><a href="timer">timer</a></li>
       </ul>
@@ -65,7 +65,7 @@
         <td>
           <ul>
             <li><a href="io">io</a></li>
-            <li><a href="process">process</a></li>
+            <li><a href="os">os</a></li>
             <li><a href="scheduler">scheduler</a></li>
             <li><a href="timer">timer</a></li>
           </ul>