feat(media-buy): add cursor pagination for bounded delivery breakdowns

[sujanchalla0510]

Closes #5671.

Summary

get_media_buy_delivery's by_<dim>_truncated flags told a buyer that a breakdown was clipped but gave no way to retrieve the dropped rows — re-requesting with a higher limit isn't a defined retrieval path. Adds reporting_dimensions.<dim>.cursor on the request and by_<dim>_pagination (reusing the existing pagination-response.json shape already used by get_products) on the response, for the four bounded-enum dimensions: device_type, device_platform, audience, placement.

geo is deliberately excluded — at postal_area granularity it can reach tens of thousands of rows, closer to a bulk-export shape than per-package cursor pagination, and is deferred to the bulk-export/security work tracked in #5669/#5666 rather than shipping a second retrieval mechanism here. This follows the most recent of three triage passes on this issue, which converged on exactly this split.

Verification

Checked the current schema directly rather than trusting the issue description: the sort/limit negotiation echo contract (by_<dim>_sorted_by/by_<dim>_sort_direction, PR #6627) already covers these same five dimensions, but its own description explicitly names #5671 (breakdown continuation) as "the complement" — confirming the gap this issue names is still live.

Tests

Added 20 new test cases to tests/sort-contract-delivery-reporting.test.cjs covering request/response schema shape and validation for all four dimensions (plus a case proving geo deliberately does not get these fields). Confirmed the tests are real: temporarily reverted the schema changes, watched the new tests fail, restored, confirmed green again.

• npm run build:schemas succeeds
• npm run test:schemas (183 tests) passes
• node scripts/check-changeset-protocol-scope.cjs origin/main passes
• npx @changesets/cli status --since=origin/main shows the expected minor bump
• node scripts/check-pr-title.cjs passes on this title

🤖 Generated with Claude Code

https://claude.ai/code/session_01VPVi4oM4fC7MLRfcFW7KzE

[aao-secretariat]

Ladon verdict: Request changes

Request changes — 1 blocking finding.

Blocking findings

• docs/media-buy/task-reference/get_media_buy_delivery.mdx:965 — Schema↔docs coherence drift: the schema adds a mandatory by_<dim>_pagination cursor contract ("Sellers MUST return") for device_type/device_platform/audience/placement in get-media-buy-delivery-response.json, but the docs Truncation section still states the contract provides no cursor. The docs assert a wire shape the schema no longer encodes — mandatory schema↔docs coherence drift, classified high per repo rules.

The additive cursor-pagination change otherwise checks out: changeset type/scope (minor, additive), pagination-response reuse, oneOf discriminator, released-artifact immutability, and the deliberate geo exclusion are all sound. The docs page under docs/media-buy/task-reference/ must be updated to reflect the new mandatory cursor contract before this can merge.

Note: this PR also touches gated paths (static/schemas/source/**) with review_decision REVIEW_REQUIRED; human/CODEOWNERS review is required regardless.

Blocking findings

• docs/media-buy/task-reference/get_media_buy_delivery.mdx:965 — Schema adds mandatory by__pagination cursor contract but docs Truncation section still states no cursor is provided; schema↔docs coherence drift (high)

[sujanchalla0510]

Fixed in 78674ce — updated the Truncation section in `docs/media-buy/task-reference/get_media_buy_delivery.mdx`, which flatly stated the truncated-flag contract "does not provide a cursor." Now documents the new retrieval path for `device_type`/`device_platform`/`audience`/`placement` while keeping the existing "analytical ranking only, no cursor" framing accurate for every other dimension (`geo` included, per its deliberate exclusion).

Generated by Claude Code

[aao-secretariat]

Ladon verdict: Escalate to human review

Escalate — gated schema paths modified without required approval.

This PR adds new bounded-enum pagination fields to two protocol schemas under static/schemas/source/** (get-media-buy-delivery-request.json and -response.json), with matching docs, a minor changeset, and a test. The reviewer's pass was clean: schema↔docs coherence holds (device_type, device_platform, audience, placement gain cursor request fields + by__pagination response fields, geo excluded), the changeset is a correct minor, and the get_products cross-reference is accurate. No Critical/High/Medium findings, so no blocking issues on content.

However, both modified files fall under a hard, deterministic approval gate (gated_paths: true) and review_decision is CHANGES_REQUESTED — not APPROVED. Per decision rule row 2, this PR cannot be approved until a human/CODEOWNERS review clears it.

Escalation reasons

• static/schemas/source/media-buy/get-media-buy-delivery-request.json (modified) — gated protocol-schema path; requires human/CODEOWNERS approval.
• static/schemas/source/media-buy/get-media-buy-delivery-response.json (modified) — gated protocol-schema path; requires human/CODEOWNERS approval.
• review_decision is CHANGES_REQUESTED; the gate is not satisfied.

Why human review

• Gated path static/schemas/source/media-buy/get-media-buy-delivery-request.json (modified) requires human/CODEOWNERS approval; review_decision is CHANGES_REQUESTED, not APPROVED
• Gated path static/schemas/source/media-buy/get-media-buy-delivery-response.json (modified) requires human/CODEOWNERS approval; review_decision is CHANGES_REQUESTED, not APPROVED
• This PR touches a path under a hard, non-overridable approval gate (static/schemas/source/media-buy/get-media-buy-delivery-request.json (modified) matches static/schemas/source/**; static/schemas/source/media-buy/get-media-buy-delivery-response.json (modified) matches static/schemas/source/**) and the current GitHub review decision is 'CHANGES_REQUESTED', not APPROVED. This is a hard gate enforced in code — Ladon cannot auto-approve until a human/CODEOWNERS approval is recorded, regardless of how clean the diff is.

[bokelley]

Human review complete at d2a3d95. The cursor contract, deliberate geo exclusion, docs, changeset, and tests are coherent; prior automated findings have been addressed.

Dismissed after the follow-up commit aligned the documentation with the pagination schema; current head has a human approval and green CI.

[bokelley]

Re-approving current head after dismissal of the superseded automated change request.