Merge branch 'stdlib-p0' into dev

Merge stdlib P0 implementation: string methods, file I/O, os module,
pathlib, json, re, argparse, math completion, itertools completion,
collections additions (OrderedDict, ChainMap), random additions.

Resolved conflicts with dev's independent module implementations by
keeping dev versions and adapting stdlib-p0 tests. Fixed Accumulate
value-type initial parameter bug, OsPath.Normpath to preserve relative
paths, and made all Itertools partial classes public.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: antonsynd

src/Sharpy.Compiler.Tests/Discovery/Caching/OverloadIndexBuilderTypeTests.cs

@@ -129,8 +129,9 @@ public void DiscoverPublicTypes_ExceptionTypes_HaveCorrectBaseTypeName()
         // Assert
         var builtins = index.Modules["builtins"];
         var exceptionTypes = builtins.Types.Where(t => t.IsException).ToList();
-        // Most exception types directly extend Exception, but some (IOError, FileNotFoundError)
-        // extend intermediate .NET exception types (IOException, FileNotFoundException)
+        // Most exception types directly extend Exception, but some (IOError, FileNotFoundError,
+        // FileExistsError, IsADirectoryError) extend IOException, FileNotFoundException,
+        // UnauthorizedAccessException, or ValueError (JSONDecodeError)
         var allowedBaseTypes = new HashSet<string?>
         {
             "Exception", "IOException", "FileNotFoundException", "UnauthorizedAccessException", "ValueError"