refactor(runtime)!: enforce durable protocol v3 boundaries

[WH-2099]

Problem

The latest Driver, Codex app-server, ACP, Claude Agent SDK, and Cloud Agent boundaries changed payloads, lifecycle behavior, generated types, process ownership, and release requirements.

The Mosoo Draft currently pins an older Driver checkpoint and does not yet validate the latest strict protocol version 3 contract.

Goal

Integrate protocol version 3 as a schema-first durable boundary across Driver ingress, runtime state, persistence, artifacts, GraphQL, AG-UI, reconnect hydration, Web UI, and deployment safety.

Current status

• Driver PR refactor(runtime)!: enforce durable SDK protocol v3 boundaries mosoo-agent-driver#112 now points to 3439bed72ad18ee6c295668117f88a66219ba45f.
• Mosoo PR refactor(runtime)!: enforce durable protocol v3 boundaries #585 still pins 5e661259e853663e561fed167aa495e792450045.
• The latest Driver checkpoint passes 1,666 tests with 0 failures and 40 explicit skips.
• The previous Mosoo integration passed 41 of 41 tasks, but that result is historical until the new Driver commit is pinned and revalidated.

Acceptance status

• Driver publishes a strict protocol version 3 contract.
• Driver latest-SDK lifecycle, cleanup, and generated bindings pass locally.
• Rebase the Mosoo Draft onto current main.
• Pin the latest durable Driver commit.
• Adapt and revalidate every Mosoo protocol version 3 boundary.
• Cloudflare Sandbox provides an atomic writer-freeze or forbidden-path backup guarantee.
• A real-content race test proves transient credentials cannot enter a backup.
• Final Mosoo CI is green before the Draft is removed.

Release constraint

Do not deploy or merge the Mosoo implementation while the Driver pin is stale or Cloudflare Sandbox cannot atomically exclude transient credential paths from backup capture.

Related work

• Mosoo Draft implementation: refactor(runtime)!: enforce durable protocol v3 boundaries #585
• Driver issue: refactor(runtime)!: enforce durable SDK protocol v3 boundaries mosoo-agent-driver#111
• Driver implementation: refactor(runtime)!: enforce durable SDK protocol v3 boundaries mosoo-agent-driver#112