feat(protocol)!: stabilize multi-version SDK 8 beta

[bokelley]

Summary

• add version-scoped public model namespaces and portable MCP schemas for AdCP 3.0, 3.1, and 3.2 beta
• derive HTTP signing from the negotiated AdCP version and require an explicit profile in low-level signing APIs
• add the semantic BrandIdentity export and document the SDK 7 to 8 / AdCP 3.1 to 3.2 migrations
• validate complete compact and proposal lifecycle surfaces without changing legacy lifecycle support

Validation

• 6,486 passed, 40 skipped, 9 deselected, 1 xfailed
• ruff, mypy, strict adopter fixtures, type-ignore contract, and pre-commit hooks pass
• wheel and sdist build; clean-wheel import and versioned schema smoke passes
• code, protocol, and test expert reviews report no release blocker

Closes #1036
Closes #1037
Addresses #911

BREAKING CHANGE: Low-level sign_request and async_sign_request calls now require an explicit signing_profile_version.

[aao-secretariat]

Ladon verdict: Approve

Approve — SDK 8 beta multi-version public models (adcp.types.v30/v31/v32), portable MCP tools/list schemas, negotiated-pin request signing, and a collision-safe BrandIdentity export.

Gate checks:

• No no-auto-approve team match.
• gated_paths: false — row 2 does not apply.
• high_risk: true but all reasons are (modified) with no medium-or-higher findings; no (deleted) entries. Rows 3/5 do not fire.
• Semver signal: the breaking low-level signer change ships under feat(protocol)! with a BREAKING CHANGE footer and migration notes (MIGRATION_v7_to_v8.md / request-signing-migration.md); the new BrandIdentity export is recorded in public_api_snapshot.json — the mandatory semver-signal requirement is satisfied.
• No Critical/High/Medium findings. Only three low-severity notes (schema_loader.py and versioned.py verified sound under largest-file coverage; a construction-time behavior change where a legacy server_version pin + SigningConfig now raises at ADCPClient construction).

No blocking findings and no escalation trigger — falls through to row 9.

Low-severity note for follow-up: client.py:682 — legacy server_version pin combined with SigningConfig now raises at construction; confirm this is documented in migration notes.

[bokelley]

Addressed the automated review follow-up in 41df3a0: the migration guides now explicitly document pre-3.0 signed-client construction behavior, with a regression test confirming unsigned legacy clients remain unaffected.

[aao-secretariat]

Ladon verdict: Approve

Approve.

The delta since the prior approve is documentation clarifications (MIGRATION_v7_to_v8.md, docs/request-signing-migration.md) plus one new conformance test asserting a signed client pinned to legacy AdCP 2.5 fails closed at construction (DeprecationWarning fired in _resolve_server_version before signing_profile_for_adcp_version raises ValueError on the unsupported '2.5' profile). Docs accurately reflect 3.0–3.2 support and construction-time failure.

No critical, high, or medium findings in this run. high_risk is true only via (modified) entries with no accompanying medium-or-higher concern, so no escalation trigger applies (rows 3–5 do not fire). gated_paths is false; no no-auto-approve team match. Prior decision was approve, so sticky escalation (row 6) does not apply. Falls through to row 9.