Reset main repo to master after non-worktree phase execution#

Problem#

After PhaseRouterService.executePhase() completes a phase that ran in the main repo (no isolated worktree), the repo can be left on a feature branch, causing subsequent phases to start from the wrong branch.

Task / Link#

Closes #267

Changes#

• Added WorktreeService.resetToMaster(repo) — runs git checkout master in the main repo path, catches errors and logs a warning without throwing
• Called resetToMaster in PhaseRouterService.executePhase() finally block when !worktreePath (phase ran in main repo, not a worktree)
• Added unit tests: resetToMaster called for non-worktree phases, not called for worktree phases, error is caught and does not propagate
• Added unit tests for WorktreeService.resetToMaster: correct git command + cwd, and failure is swallowed with a warning

Notes#

If the main repo has uncommitted changes at cleanup time, git checkout master will fail — the error is caught and logged as a warning so the original phase result is not masked.

Testing#

• npm run test — 694/694 tests pass
• npm run lint — zero errors