Platform-gate the main-checkout identity compare in worktree removal

Copilot on #3574: the guard lowercased both paths unconditionally while
find_worktree ten lines up gates the case fold on Windows - on a
case-sensitive filesystem, case-differing paths were wrongly equated and
a legitimate deletion refused as "main". Same gate as the sibling now.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012kHBtxNVFeNDxBphkfUAzg

Author: borisbat

utils/dasHerd/watcher/repository_core.das

@@ -755,7 +755,13 @@ def public repository_remove_worktree(repository_id, worktree_path : string;
     }
     var runtime = g_repositories[repository_index]
     let checkout = runtime.snapshot.record.checkout_path
-    if (to_lower(normalized_path(worktree_path)) == to_lower(normalized_path(checkout))) {
+    // Case-insensitive only on Windows, matching find_worktree's platform
+    // gate - a case-sensitive filesystem holds case-differing paths apart.
+    let wanted_identity = (get_platform_name() == "windows"
+        ? to_lower(normalized_path(worktree_path)) : normalized_path(worktree_path))
+    let checkout_identity = (get_platform_name() == "windows"
+        ? to_lower(normalized_path(checkout)) : normalized_path(checkout))
+    if (wanted_identity == checkout_identity) {
         reason = "main"
         detail = "the main checkout cannot be deleted"
         return false