When EnterWorktree creates a branch from main instead of the current HEAD
(a known issue on Windows), executor agents now detect the mismatch and
reset their branch base to the correct commit before starting work.
- execute-phase: capture EXPECTED_BASE before spawning, inject
<worktree_branch_check> block into executor prompts
- execute-plan: document Pattern A worktree_branch_check requirement
- quick.md: inject worktree_branch_check into executor prompt
- diagnose-issues: inject worktree_branch_check into debugger prompts
- settings: add workflow.use_worktrees option so Windows users can
disable worktree isolation via /gsd:settings without editing files
Closes#1510
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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