fix: address kiloconnect review comments on commit message generation

- Use trimEnd() instead of trim() in git() to preserve leading whitespace
  in porcelain output (fixes status parsing for ' M file' lines)
- Remove unused 'untracked' from FileChange status union
- Use repository.rootUri.fsPath instead of workspaceFolders[0]
- Add explicit null-check for client after try/catch
- Fix test mocks: add isActive/activate, use mockImplementation to throw,
  fix expected error message to match production code

packages/opencode/src/commit-message/git-context.ts

@@ -134,7 +134,7 @@ function git(args: string[], cwd: string): string {
     stdout: "pipe",
     stderr: "pipe",
   })
-  return result.stdout.toString().trim()
+  return result.stdout.toString().trimEnd()
 }
 
 function parseNameStatus(output: string): Array<{ status: string; path: string }> {