fix(opencode): improve removeEmptyParents error handling and loop clarity

- Distinguish recoverable errors (ENOTEMPTY, ENOENT) from fatal errors in
  removeEmptyParents() catch block — skip level and continue upward on
  TOCTOU races or concurrent removal, break only on fatal errors (EACCES)
- Add comment clarifying loop invariant for missing-path continue branch

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

tools/cli/installers/lib/ide/_config-driven.js

@@ -557,14 +557,21 @@ LOAD and execute from: {project-root}/{{bmadFolderName}}/{{path}}
       if (!fullPath.startsWith(resolvedProject + path.sep) && fullPath !== resolvedProject) break;
       try {
         if (!(await fs.pathExists(fullPath))) {
+          // Dir already gone — advance current; last is reset at top of next iteration
           current = path.dirname(current);
           continue;
         }
         const remaining = await fs.readdir(fullPath);
         if (remaining.length > 0) break;
         await fs.rmdir(fullPath);
-      } catch {
-        break;
+      } catch (error) {
+        // ENOTEMPTY: TOCTOU race (file added between readdir and rmdir) — skip level, continue upward
+        // ENOENT: dir removed by another process between pathExists and rmdir — skip level, continue upward
+        if (error.code === 'ENOTEMPTY' || error.code === 'ENOENT') {
+          current = path.dirname(current);
+          continue;
+        }
+        break; // fatal error (e.g. EACCES) — stop upward walk
       }
       current = path.dirname(current);
     }