## What changed
- Replace the upstream V8 module and dependency bridge with a source repository rule and `third_party/v8/engine.BUILD.bazel`, wiring dependencies and Python generator inputs directly from Codex.
- Import source filegroups from the pinned upstream BUILD, rejecting missing boundaries, malformed sections, and unexpected compiled targets.
- Define fixed source feature selections in the engine BUILD while retaining release ABI, runtime, and CPU settings. Reuse upstream platform configuration and limit the build integration patch to `bazel/defs.bzl`.
- Document source inventory review and canary validation for V8 upgrades.
GitOrigin-RevId: 1b42672b77fb8f0f34c41ae3345c0e302a892d44