[cookerpapa]

Fixes #614.

Runtime V2 treats an empty parsed step list as complete. A prompt with ## Step headings, or no step headings at all, can therefore succeed without launching a worker and receive a .DONE marker.

This change rejects zero-step prompts before worker launch and rechecks the prompt during execution and before finalization. The runner returns a failed outcome, records the required ### Step N: ... format in STATUS.md, and quarantines any existing completion marker. It preserves accumulated worker telemetry and allows valid, already-completed tasks to resume without spawning another worker.

Validation on Node 24 / Linux:

• Ten behavioral regression tests pass. Nine reproduce false success on the unmodified base; the completed-task resume case passes before and after. Tests exercise the real lane runner and file operations, with worker spawning mocked.
• The upstream CI test selection passes: 3,611 tests, no skips.
• Full suite: 4,106 passed, 6 failed. The unmodified base has the same six failures: Windows-path checks and the project-config-loader base-agent lookup. These files are already excluded by the upstream CI workflow.
• Typecheck, lint and format checks pass. Task/status references and their relative links are updated and checked.

Base: 293d9a833ba685d4c2291a1d68e9b68b0271e00a. No live pi session was used for this validation.