feat: emit qualified entity decision tasks v2

[abrichr]

Summary

• Add optional qualification-owned entity class labels and qualify label set/remove/list.
• Emit signed HumanDecisionTaskV2 only after explicit remote peer schema negotiation.
• Send a reviewed remote-safe class when one exists. Keep custom classes local and send only their signed neutral record or item fallback.
• Use the released openadapt-types 0.9 contract.
• Consolidate the optional-label behavior from fix: keep entity labels optional in decision v2 #314, the corrected documentation from docs: describe V2 qualified decision labels #309, and the neutral shared language from docs: use neutral entity language in shared guidance #311.

Qualification and safety

V2 requires:

• A current passed qualification certification.
• Exact project revision and project, workflow, and policy contracts.
• The exact failed step and open pause capability.
• The exact current bundle version.
• Explicit peer support for openadapt.human-decision-task/v2.

The entity label is optional and never blocks qualification, certification, or execution. A label change revises the qualification contract and invalidates certification. The producer does not derive a class from screenshots, OCR, accessibility data, parameters, application names, or models.

A reviewed class can cross the remote boundary. A custom class remains local. Its signed neutral fallback crosses instead. A missing class uses signed neutral record. If any authority or negotiation gate fails, Flow emits the byte-compatible V1 task.

Validation

• 230 focused attended-action, qualification, and business-decision tests pass.
• 38 interop and learning-gate tests pass.
• Ruff passes on all touched Python files.
• MyPy passes on the touched safety modules.
• Release consistency passes with Flow 1.30.0 and openadapt-types 0.9.0.

This PR remains a draft until exact-head CI and independent review approve the consolidated head. Do not merge or close #309, #311, or #314 before that review confirms that their intended changes are present here.