Orchestrate managed native generation services

[brxs]

Summary

• route SA3 and MRT2 through verified app-managed native services
• retain process-tree ownership across readiness, restart, cancellation, and promotion failures
• authenticate local IPC and expose atomic connection snapshots
• add a bounded MRT2 render protocol and model-family routing
• qualify managed-runtime behavior on native Windows, including a real Job Object descendant tree and fail-closed promotion while reap status is uncertain

Stack

• based on fix: prove managed runtime candidates are self-contained #134
• incorporates the reviewed render protocol from Add bounded MRT2 render worker protocol #133
• intended for the final Add cross-platform runtime and Windows/Linux shipping #131 integration branch after this exact head passes hosted Windows qualification

Local validation

• clean frontend install/build, lint, and 666 tests
• default and managed-runtime Rust suites
• strict Clippy for default and managed-runtime features
• portable Python/backend matrices and render-protocol tests

Required hosted gate

The new windows-2025 job must pass at this exact head. It runs managed-runtime tests, Clippy, release build, authenticated Rust↔Python framing, real Job Object tree teardown, atomic promotion after positive reap, and the negative uncertain-reap/no-rename proof.

Tracks #107.

[brxs]

Superseded by and fully consolidated into #131. The combined branch includes this lane's substantive changes, subsequent integration fixes, and exact-head cross-platform validation. Please continue review in #131.