feat(testing): signals/creative-delivery/creative-features seeded bridges (#1755 phase 3)

[bokelley]

Phase 3 of #1755 — extends TestControllerBridge with the next batch of read-path bridges so platform-proxy sellers can seed signal + creative fixtures into compliance storyboards without driving real upstream calls.

Summary

Bridges shipped (3)

Bridge	Tool	Shape	Specialism(s) unblocked
getSeededSignals	get_signals	list-merge by signal_id (canonical)	signal-marketplace, signal-owned (one bridge handles both — signal_type is the per-entry discriminator)
getSeededCreativeDelivery	get_creative_delivery	list-merge by creative_id, pagination.total drift	creative-ad-server, creative-template, creative-generative (delivery readback)
getSeededCreativeFeatures	get_creative_features	merge into success-arm results[] by feature_id (oneOf-aware no-op on error arm)	creative-* governance feature evaluation

Bridges skipped (2 — schemas don't exist in 3.0.11)

• list_audiences — not a 3.0.11 tool. Audience discovery is folded into sync_audiences (the discovery-only call omits the request audiences array but still returns audiences[]). See src/lib/testing/storyboard/default-invariants.ts:725-727 and the absence of any audiences/ directory under schemas/cache/3.0.11/bundled/.
• list_targeting_categories — not a 3.0.11 tool. Targeting capabilities surface via get_adcp_capabilities. No list-targeting-*.json schemas exist under schemas/cache/3.0.11/.

Schema citations

• schemas/cache/3.0.11/bundled/signals/get-signals-response.json — signals: [{ signal_id, ... }], dedup key signal_id (discriminated union: {source:'catalog', data_provider_domain, id} or {source:'agent', agent_url, id} — canonical dedup key is ${source}|${origin}|${id}).
• schemas/cache/3.0.11/bundled/creative/get-creative-delivery-response.json — creatives: [{ creative_id, ... }], optional pagination.total (field name total, distinct from total_count elsewhere).
• schemas/cache/3.0.11/bundled/creative/get-creative-features-response.json — oneOf envelope. Success arm: results: CreativeFeatureResult[] (dedup key feature_id); error arm: errors: Error[]. No top-level entity id.

Implementation notes

• get_creative_features is the first nested-array bridge. The seeded array (CreativeFeatureResult[]) merges into a property of the success arm (results), not the top-level response. The handler computes everything else; the bridge just augments per-feature evaluations. Error arm is a no-op (the seeded results array can't be grafted onto an error envelope without producing a wire-incorrect mixed shape).
• Signal id is a discriminated union. SignalID is {source:'catalog', data_provider_domain, id} or {source:'agent', agent_url, id} — two signals with the same id from different sources are distinct, so dedup keys on the full tuple. Validation drops entries with malformed source/origin/id triples.
• Triply-gated dispatch + seeded-wins on collision preserved across all three bridges (matches the existing precedent from feat(testing): getSeededMediaBuyDelivery bridge callback + nit tests (#1755 phase 1) #1759 / feat(testing): governance/property-lists/content-standards/collection-lists seeded bridges (#1755 phase 2) #1761).
• get_creative_features envelope fields preserved. context, ext, detail_url, pricing_option_id, vendor_cost, currency, consumption round-trip from the handler verbatim — only results is augmented.

bridgeFromSessionStore selectors added

• selectSeededSignals
• selectSeededCreativeDelivery
• selectSeededCreativeFeatures

Omitted selectors leave the corresponding bridge callback unset (opt-in by presence, same pattern as existing selectors).

Documentation

docs/guides/VALIDATE-YOUR-AGENT.md "Platform-proxy sellers" table extended with the three new entries, plus a new bullet documenting get_creative_features's oneOf-aware nested-array merge semantics.

Test plan

• 28 new wiring tests in test/lib/seed-per-tool-wiring.test.js:
  • signals (8 tests): seeded-only, handler-only, canonical collision, mixed collision, catalog/agent same-id distinct, sandbox refusal, invalid signal_id drop
  • creative-delivery (8 tests): seeded-only, handler-only, append-merge, collision, mixed collision, pagination.total append + collision no-drift, sandbox refusal, validation drop
  • creative-features (8 tests): merge into results, handler-only, collision, mixed collision, error-arm no-op, envelope-fields preserved (context/ext/detail_url/vendor_cost), sandbox refusal, validation drop
  • bridgeFromSessionStore wiring (4 tests): three selectors wire matching callbacks; absent selectors omit them
• Total wiring suite: 58 → 115 (115 pass, 0 fail).
• npm run typecheck clean
• npm run format:check clean
• Full npm test from root: 8745 pass, 3 skipped, 0 fail (+ eslint-plugin workspace 30/30 pass)

[bokelley]

Review nits addressed

Three small fixes from the code-review + protocol-expert reviews:

• JSDoc correction: getSeededSignals previously claimed PaginationResponse has no total_count; that's wrong. The field exists but isn't recomputed on partial-page merges (justification updated in the JSDoc).
• sandbox stamp: mergeSeededCreativeDeliveryIntoResponse now stamps sandbox: true for consistency with mergeSeededSignalsIntoResponse.
• Changeset accuracy: summary no longer lists skipped audiences/targeting tools.