AdCP 3.3: mutation_outcome on errors and unsupported-targeting-dimension details #1642

Spec

1. core/error.json can carry mutation_outcome (not_applied, unknown, applied), so a buyer knows whether to re-plan after a failed state-changing request. See L3 error-handling §Mutation outcome.
2. UNSUPPORTED_FEATURE for an unsupported or removed targeting dimension SHOULD carry the new error-details/unsupported-targeting-dimension.json details (unsupported_dimension, optional supported_dimensions, deprecated, replacement_dimension, product_id, package_index), with error.field pointing at the targeting path (#8052).

Tag v3.3.0-beta.0; What's new §Did a failed mutation apply? and §Optional declarations.

Work (after regen)

• AdcpError(mutation_outcome=...) and projection through MCP, A2A and the payload errors[].
• The framework sets not_applied where it knows the mutation never ran: validation, auth, idempotency conflicts, pre-dispatch rejections.
• A typed constructor for unsupported-targeting-dimension details.
• Buyer: expose mutation_outcome on TaskResult errors.
• Gate both for callers below 3.3 if a 3.2 schema rejects them.

Batch: C (needs regen).