fix(protocol): support AdCP 3.1.14 schemas

[bokelley]

Summary

• update the bundled protocol schemas and generated Python types from AdCP 3.1.13 to 3.1.14
• adopt the canonical enum references restored upstream for protocol badges, sponsored catalog types, and trusted-match surfaces
• add regression coverage for the new measurement, promotion, and linear_tv values
• expand the SDK 6 to 7 migration guide from its initial creative/webhook notes into a complete upgrade guide
• document all stable 7.0 breaking changes with verified code examples
• add security, tenant-isolation, callback, and staged-rollout guidance
• update the README description so adopters can find the broader guide

Why

AdCP 3.1.14 is a schema-correction release that replaces three inline enum copies with their canonical definitions. The generated 7.0 changelog also split user-facing SDK changes across three release candidates and the stable release. This PR keeps the 7.x line current with the latest stable AdCP 3.1 patch and gives adopters one complete migration page to follow.

Developer impact

Adopters upgrading from any SDK 6.x release now have explicit instructions for:

• canonical and intentionally legacy creative APIs
• required roster authorization callbacks
• custom decisioning executor admission limits
• dedicated PostgreSQL advisory-lock pools
• synchronous webhook behavior
• fail-closed callbacks and tenant-scoped state

The schema update additionally accepts:

• measurement as a registry badge protocol role
• promotion as a sponsored-placement catalog type
• linear_tv as a trusted-match surface

Validation

• verified the upstream v3.1.14 archive checksum and Sigstore provenance before regeneration
• 32 passed across the 3.1.14 regressions, schema-version pin, signing-vector completeness, and code-generation tests
• full suite: 6383 passed, 41 skipped, 1 xfailed; one unrelated wall-clock benchmark exceeded its five-second budget under load, then passed in isolation
• make validate-generated
• ruff check tests/test_adcp_3_1_14_schema_backport.py
• imported every documented Legacy* type and verified each documented client method
• inspected runtime signatures for create_roster_account_store, decisioning serve, PgBackend, and IdempotencyStore
• pre-commit hooks across every changed file
• git diff --check

[aao-ipr-bot]

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