feat: add schedule worktree isolation for running jobs in isolated worktrees

[chriswritescode-dev]

Adds schedule worktree isolation, allowing scheduled jobs to run in isolated git worktrees instead of inline in the main working directory. Includes:

• New isolationMode field (worktree/inline) and optional branch field on schedule jobs
• ScheduleWorktreeManager service for worktree lifecycle (create, finalize, teardown)
• Migration 014-schedule-worktree-isolation adding runBranch, commitHash, and worktreePath columns to schedule_runs
• Branch/commit metadata displayed in run history cards and job detail tab
• UI controls in GeneralTab for isolation mode and branch selection
• Race-safe teardown guard to prevent duplicate finalization
• Recovery logic for orphaned runs with worktree paths

Checks

• pnpm lint