feat(cli): add a fail-closed --cancel-worktree command that safely tears down a cancelled agent's leased workspace (#230)

[qwen-code-dev-bot]

Summary

Adds an opt-in (--cancel-worktree) fail-closed command that safely tears down a cancelled agent's leased workspace, decomposed from roadmap #39 (isolated parallel agents).

cleanWorktreeLease (#50) only cleans a lease after its work is verified complete and merged; nothing defined the safe teardown path for an agent cancelled mid-work, so a naive cancellation could leave a dangling worktree, an unreleased lease, or silently discard committed work.

Design

• src/worktree-lease.ts: new cancelWorktreeLease(opts, { force }) (reusing the module's identity/git helpers) plus formatWorktreeCancelResult. Unlike cleanWorktreeLease, cancellation preserves committed work by keeping the lease branch (reporting the preserved, bounded/redacted commits for later integration via Parallel integration: reviewably integrate a parallel agent's branch into the target, preserving commit identity and failing closed on conflict or dirty state #228) and only removing the worktree. It fails closed on uncommitted changes unless force acknowledges the discard, is idempotent (cancelling an absent lease is a no-op), and never touches the parent worktree.
• src/index.ts: opt-in --cancel-worktree with --cancel-force, wired into the existing leased-worktree mode (JSON + text), exiting 0 on success, 1 on a safety refusal, and 2 on a usage/git error.

Testing

• tests/unit/cancellation-cleanup.test.ts (8 tests): clean cancellation (worktree removed, branch preserved), preserved-commit reporting, fail-closed on uncommitted work, --cancel-force discard, idempotent no-op on an absent lease, missing-identity refusal, and formatting.
• tests/integration/cancellation-cleanup.test.ts (4 tests): CLI cancels a clean lease (worktree removed, branch preserved), refuses a dirty lease without --cancel-force (exit 1, worktree retained), discards with --cancel-force (exit 0), and rejects combining --cancel-worktree with --clean-worktree (exit 2).

Gates: typecheck, build, unit (1647), integration (455 + desktop), smoke (51) all pass.

Closes #230

[qwen-code-dev-bot]

E2E verification

• Repository: qwen-code-dev-bot/oh-my-cli
• Pull request: #231
• Commit: 8cfc25a26e864c1cbd47d5ede5005af8d14d0e19
• Evidence mode: terminal
• Result: PASS

Scenario	Command	Exit	Duration
integration	npm run test:integration	0	30.068s
smoke	npm run smoke	0	3.267s

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