feat(training): add deterministic typed proposal negotiation profiles

[bokelley]

Goal

Turn the public training seller from ask-only proposal refinement into a deterministic environment where buyer-agent and seller-agent implementors can exercise the complete AdCP 3.2 negotiation lifecycle.

Parent program: #6556
Protocol implementation: #6547

Profiles

Keep the existing ask-only profile and add capability-distinct profiles such as:

1. Typed negotiation: supports total_budget, product_changes, criteria, and alternatives, with max_alternatives: 3.
2. Constrained seller: supports the same dimensions but has deterministic commercial floors, product conflicts, targeting effects, and fewer available alternatives.
3. Finalization failure: exercises atomic hold creation, expiry, retry, and rollback.

Acceptance criteria

• Consume the proposal-negotiation primitives from @adcp/sdk; do not maintain a second incompatible validator/orchestrator.
• Use deterministic fixture policy rather than an LLM as the source of commercial truth.
• Produce valid revised, partial, unable, and finalized outcomes with all reason codes reachable through documented scenarios.
• Preserve immutable proposal lineage and never mutate source snapshots.
• Apply capability and cardinality preflight to the entire request before mutation.
• Support exact idempotent replay and reject changed payloads under a reused key.
• Stage writes until response validation passes; finalize batches create every hold or none.
• Expose a stable scenario/config selector usable by SDK integration tests, storyboards, and certification labs.

Required end-to-end scenario

• Buyer discovers a three-alternative ceiling.
• Buyer requests a USD 50,000 cap, product include/omit changes, US/Canada criteria, and three alternatives.
• Seller returns two valid drafts with partial / alternatives_unavailable.
• Buyer retries with two, selects one, finalizes it, and accepts before expiry.
• Buyer later creates an amendment and a cancellation proposal without mutating the accepted source.

Tests

• Cover all typed dimensions and reason codes.
• Cover task-wide unsupported-dimension rejection with no sibling mutation.
• Cover 10-alternative and 25-refinement boundaries.
• Cover missing/wrong-currency/out-of-range budgets, duplicate digests, partial counts, missing sources, replay, expiry, and atomic finalize failure.

Dependencies

• feat(media-buy): structure proposal refinement negotiation #6547 merged and released in the development schema bundle.
• TypeScript SDK work tracked from epic: make proposal negotiation easy to implement, teach, and verify #6556 is available for consumption.

Additional scope (contract hardening in #6547, efe48f522e)

• The typed-negotiation profile should also advertise and implement cpm, impressions, and flight (all now schema-defined and validator-checked); note the capability dimension is product_changes, not product_selection.
• The deterministic engine must classify per the precedence rule: constraint_unsatisfiable wins over alternatives_unavailable/uninterpreted; typed failures never surface as commercially_declined.
• Finalize paths: simulate hold_unavailable (inventory sold since drafting, hold-policy cap) and batch_aborted siblings in the atomic batch; enforce a concurrent-hold cap per buyer as the reference for the documented squatting defense; double-finalize returns INVALID_STATE (already shipped for the ask-only profile).
• The response validator now enforces recomputed terms_digest, distinct commercial_terms across alternatives, and parent_proposal_id = source on every successor — profile outputs get this for free but must not fight it.
• partial outputs must honor the invariant that unlisted constraints are satisfied by every returned draft.

[bokelley]

Triage

Classification: Feature request
Bucket(s): spec-adjacent enablement, training / certification
Status: deferred

Blocked-on: #6547 — resurfaces on merge.

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Triaged by Claude Code. Session: https://claude.ai/code/session_018RGoDTuiqz6KR42uXmLEAy

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Generated by Claude Code