fix(schema): align brand property type enums

[bokelley]

Summary

• replace stale inline brand property enums with the canonical property-type schema reference
• align single and bulk brand-claim verification schemas so linear_tv and ai_assistant validate consistently
• update protocol and implementation docs, including copyable TypeScript and Zod validators
• add bidirectional schema coverage for all canonical values and rejection of non-canonical values

Fixes #6330

Testing

• npm run build:schemas
• npm run test:schemas (29 schema checks and 4 metadata checks passed)
• targeted snippet and JSON-schema validation for all three changed docs
• node scripts/check-changeset-protocol-scope.cjs origin/main
• npx --yes @changesets/cli@^2.31.0 status --since=origin/main
• git diff --check origin/main...HEAD

Release

Includes a minor adcontextprotocol changeset because the published schemas gain two existing canonical enum values.

[aao-secretariat]

Ladon verdict: Escalate to human review

Escalate — gated schema paths require human/CODEOWNERS review.

This PR modifies published protocol source under static/schemas/source/** (a hard-gated path), and review_decision is REVIEW_REQUIRED — not APPROVED. Per decision rule row 2, the gate is not satisfied and the outcome must be escalate.

The change itself looks clean per the reviewer: it aligns brand property.type across brand.json and the two verify-brand-claim request schemas by $ref'ing the canonical property-type enum (adding linear_tv and ai_assistant), updates all three doc surfaces to match, ships a correct minor changeset, and adds a test covering every canonical value plus a negative case. The reviewer reports schema↔docs coherence holds and the change is additive/Normative (non-breaking), with no findings. But no blocking findings does not lift the deterministic path gate — only a real APPROVED review does.

Escalation reasons

• Modifies gated schema source static/schemas/source/brand.json, static/schemas/source/brand/verify-brand-claim-request.json, and static/schemas/source/brand/verify-brand-claims-request.json; review_decision is REVIEW_REQUIRED. Human/CODEOWNERS approval is required before merge.

Why human review

• Modifies gated schema source under static/schemas/source/** (brand.json, verify-brand-claim-request.json, verify-brand-claims-request.json) while review_decision is REVIEW_REQUIRED — human/CODEOWNERS approval required (decision rule row 2).
• This PR touches a path under a hard, non-overridable approval gate (static/schemas/source/brand.json (modified) matches static/schemas/source/**; static/schemas/source/brand/verify-brand-claim-request.json (modified) matches static/schemas/source/**; static/schemas/source/brand/verify-brand-claims-request.json (modified) matches static/schemas/source/**) and the current GitHub review decision is 'REVIEW_REQUIRED', 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.