task state helper can silently rewind work to queued #366

Observed behavior

_taskboardlib.set_state(text, target, queued, today) is publicly documented as accepting queued, in_progress, or done. Calling it on an in-progress or done task rewinds the marker to [ ] and strips the lifecycle date.

The sanctioned taskwrite CLI exposes only start and done, so this is not reachable through the public task command and does not block #364. It remains an internal API/state-machine inconsistency.

Why investigate

The forward lifecycle is queued -> in-progress -> done. A silent rewind can erase start/completion evidence if another internal caller uses the advertised queued target.

Acceptance criteria

• Decide whether queued is a sanctioned repair transition or unsupported target state.
• If unsupported, reject it without mutation and narrow the public helper contract.
• If supported, document the repair semantics and make commit classification/audit behavior explicit.
• Add regressions for in-progress and done inputs.
• Preserve fail-soft behavior for malformed hook input.

Provenance

Harvested as a LOW, inherited, non-blocking finding during independent review of #364.