update-v8-version

# Update V8 Version ## Core Workflow 1. Read `third_party/v8/README.md` and follow its version-bump sequence. Treat that document as the release-process source of truth. 2. Inspect and update the concrete repo surfaces that carry the pin: - `codex-rs/Cargo.toml` - `codex-rs/Cargo.lock` - `MODULE.bazel` - `third_party/v8/BUILD.bazel` - `third_party/v8/README.md` - the matching `third_party/v8/rusty_v8_<version>.sha256` manifest when the remaining prebuilt inputs change 3. Keep the existing checksum helpers in the loop: ```bash python3 .github/scripts/rusty_v8_bazel.py update-module-bazel python3 .github/scripts/rusty_v8_bazel.py check-module-bazel python3 -m unittest discover -s .github/scripts -p test_rusty_v8_bazel.py ``` 4. Validate the release-candidate path before broadening the work: - Prefer checking the `v8-canary` CI result for the candidate branch or PR when one exists, using GitHub check tooling or `gh` as appropriate. - If CI is unavailable or the user asked for a local-only check, run the closest local validation that is practical for the changed surface and say explicitly that it is a local substitute, not the full hosted canary. 5. If the canary path passes, stop there. Summarize the result and encourage the user to commit the candidate changes or proceed with the release flow they requested. Do not publish tags, releases, or pushes unless the user asked. ## Failure Path Enter this path on...