feat(compliance): audience_buy_flow + event_dedup_flow capability-gated scenarios (#4637)

[bokelley]

Summary

Two new capability-gated scenarios in the contract pattern (#4637), both added to sales-non-guaranteed.requires_scenarios, plus a training-agent fix that unblocks one of them.

media_buy_seller/audience_buy_flow

Gated on media_buy.audience_targeting presence (not on the audience-sync specialism — option B from the RFC chat: a DSP can accept buyer-uploaded CRM lists in targeting_overlay without claiming the full audience-sync discovery/deletion lifecycle). Certifies:

1. sync_audiences returns an audience_id valid as a binding target in targeting_overlay.audience_include[].
2. create_media_buy with targeting_overlay.audience_include referencing the registered audience is accepted.
3. create_media_buy with audience_include referencing an unregistered id is rejected (INVALID_REQUEST with error.field set to the literal JSONPath-lite path packages[0].targeting_overlay.audience_include[0]) — silent acceptance would mean the seller cannot actually restrict delivery to the buyer's audience.
4. Delivery reporting surfaces totals.impressions for the audience-targeted buy. Per-audience attribution breakdown is intentionally deferred (not first-class in delivery-metrics.json today).

Sibling to media_buy_seller/performance_buy_flow on the audience side — the unbound-id rejection is the discriminating assertion, modeled on the event_source_id contract from #4642.

media_buy_seller/event_dedup_flow

Gated on media_buy.conversion_tracking.multi_source_event_dedup equals true. Certifies that the same event_id from two registered event sources attributes to one conversion, not two:

1. sync_event_sources accepts two sources (pixel + CAPI) sharing event_types.
2. create_media_buy accepts an event-kind goal whose event_sources array contains BOTH ids.
3. Two log_event calls with the SAME event_id from each source both succeed at the API level (dedup is attribution-time, not ingestion-time).
4. get_media_buy_delivery reports totals.conversions equal to 1, not 2.

The training agent does not declare multi_source_event_dedup: true (verified in v6-sales-platform.ts), so this scenario grades not_applicable against the training agent in CI — no training-agent fix is needed. The scenario only runs against sellers that explicitly opt in.

Training-agent fix (audience_buy_flow only)

create_media_buy now rejects targeting_overlay.audience_include / audience_exclude entries whose audience_id was never registered via sync_audiences, with INVALID_REQUEST and error.field set to the literal JSONPath-lite path. Mirrors the event_source_id validation pattern from #4654. Implementation:

• New server/src/training-agent/audience-handlers.ts with the in-memory store + handleSyncAudiences.
• sync_audiences wired into the legacy /mcp HANDLER_MAP and the v6 /sales/mcp AudiencePlatform.
• Validation block in handleCreateMediaBuy walking each package's targeting_overlay.audience_include[] and audience_exclude[] against the audience store.

Four unit tests in server/tests/unit/training-agent.test.ts cover the four contract paths: rejects/accepts × include/exclude.

Refs

• RFC: performance-sales specialism — is conversion-driven selling distinct from sales-social? #4569 — original capability-gating contract pattern
• Meta: capability-claim contract scenarios — close the gap between what agents declare and what they do #4637 — this PR's tracking issue
• feat(compliance): performance_buy_flow scenario for capability-gated CPA buys (closes #4569) #4642 — performance_buy_flow precedent
• fix(training-agent): event_source validation + cost_per_acquisition for performance_buy_flow #4654 — training-agent event_source_id validation precedent
• RFC: capability gating for product-level capabilities (reach / clicks / completed_views storyboards) #4651 — blocks the three product-level sibling scenarios (reach, clicks, completed_views)

Test plan

• npm run build:schemas clean
• npm run build:compliance — all 12 lints pass; new scenarios in dist/compliance/latest/protocols/media-buy/scenarios/
• npx tsc --project server/tsconfig.json --noEmit clean
• npx vitest run server/tests/unit/training-agent.test.ts — 376/376 pass (includes 4 new audience contract tests + updated tool-count assertion)
• Storyboard grader run against the training agent — audience_buy_flow should grade passed, event_dedup_flow should grade not_applicable

Scenario design notes

• error.field uses literal value: only, not matches: regex — field_value doesn't support regex and the field is JSONPath-lite per core/error.json.
• No per-audience or per-event-source delivery breakdown asserted — neither is first-class in delivery-metrics.json today. Both will land as follow-up scenarios gated on sub-capability bits.
• audience_exclude follows the same binding contract but is exercised only via unit tests, not a separate scenario phase — one positive + one negative on audience_include is the discriminating signal in YAML.
• No modification of audience-sync specialism storyboard or its index.yaml.
• No modification of performance_buy_flow.yaml — reference only.
• The training agent intentionally does not declare multi_source_event_dedup — keeping it honest as a "doesn't claim what it can't do" reference is the right state.

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