compliance(media-buy): add typed proposal negotiation storyboard matrix

[garvitkaushik-123]

Summary

• Add typed_proposal_negotiation.yaml — a 15-phase compliance storyboard exercising the complete AdCP 3.2 typed proposal negotiation lifecycle through refine_proposals
• Register the scenario in the media-buy seller index.yaml

Coverage

Phase	What it tests
Capability discovery	proposal_refinement.supported_dimensions gate
Typed budget — satisfied	revised outcome with total_budget constraint met
Typed budget — unsatisfied	partial/unable with constraint_unsatisfiable and unsatisfied_constraints
Product changes	include/omit map checked against commercial_terms.purchases
Alternatives	Exact count with unique terms_digest values
Unsupported dimension	Task-level UNSUPPORTED_FEATURE with unsupported-refinement-dimension.json details
Finalize	Committed snapshot with expires_at inventory hold
Idempotent replay	Same idempotency_key returns cached replayed: true response
Accept	proposal_terms_digest-verified acceptance creating a MediaBuy
Amendment	Draft amendment successor from accepted source
Cancellation	Draft cancellation successor from accepted source
Double-finalize	INVALID_STATE rejection for committed proposals
Multi-source batch	Ordered results with independent per-source outcomes
Immutable lineage	parent_proposal_id equals source_proposal_id on every successor

Design decisions

• Gated on proposal_refinement.supported_dimensions presence — legacy sellers without typed negotiation are not penalized
• Per-dimension phases use requires_capability with contains so sellers declaring a subset of dimensions skip inapplicable phases
• Unsupported dimension phase uses skip_if to avoid false failure when the seller does support flight
• Sample requests use the Acme Outdoor test kit identity consistent with existing storyboards

Test plan

• Storyboard context-output path lint: clean (167 files scanned)
• Storyboard validations path lint: clean (167 files scanned)
• Storyboard scoping lint: all 11 refine_proposals steps carry account { brand, operator }
• Schema validation: all 30 tests pass
• Composed schema validation: all 400 tests pass
• YAML parses correctly: 15 phases, all steps well-formed

Refs #6559

[aao-secretariat]

Ladon verdict: Request changes

Request changes — 1 blocking finding.

Blocking findings

• static/compliance/source/protocols/media-buy/scenarios/typed_proposal_negotiation.yaml:509 — Lifecycle tail (finalize/accept/amendment/cancellation/double-finalize/multi-source) depends on context outputs produced only inside a total_budget-gated phase. A spec-valid seller lacking that dimension breaks the scenario or silently loses the storyboard's headline coverage — a reproducible bug on a load-bearing compliance path.

Medium findings

• None.

The rest of the PR is solid: schema↔docs coherence is clean (asserted fields, enums, error codes, and the singular-proposal vs array-proposals split all match refine-proposals-response.json, proposal-refinement.json, canonical-proposal.json, and the capabilities schema), and the refine/decline scoping exemption is correct since the split schemas forbid account. Three low-severity narrative/checkbox nits (lines 578, 760, and the changeset test-plan) are noted but non-blocking. Address the capability-gated dependency at line 509 so the tail either guards on the gating dimension or does not rely on outputs a conformant seller may never produce.

Blocking findings

• static/compliance/source/protocols/media-buy/scenarios/typed_proposal_negotiation.yaml:509 — Lifecycle tail depends on context outputs from a capability-gated (total_budget) phase; a spec-valid seller without that dimension breaks or silently loses headline coverage

[aao-secretariat]

Ladon verdict: Approve

Approve — prior High finding resolved, no current blocking or Medium findings.

This is a subsequent review. The prior run (request-changes) flagged one High finding: the finalize lifecycle tail depending on context outputs from a capability-gated phase (typed_proposal_negotiation.yaml:509). The developer has resolved it:

• finalize_idempotency_key generation moved to the ungated seed_proposals phase (L347-348)
• finalize now targets the ungated seed_proposal_id (L655/L682/L686)
• multi_source_batch's second source now uses the ungated amendment_proposal_id (L900)

The now-orphaned budget_revised_* captures are harmless since context-output lints validate path resolution only. Net improvement over the prior pass.

Decision-table walk: no critical/high findings (row 1 no). gated_paths is false, so row 2 does not apply despite review_decision being CHANGES_REQUESTED — that stale GitHub status predates the fix and row 2 only fires when gated_paths is true. high_risk is false (rows 3, 5 no). No medium findings (rows 4, 8 no). Prior decision was request-changes, not escalate (row 6 no). No no-auto-approve team match (row 7 no). Falls through to row 9 → approve.