## Why
Artifact checksums alone do not authenticate the downloaded checksum manifest. V8 downloads need a trusted digest recorded in the repository, and published releases should not have their assets overwritten.
## What changed
- Pin the V8 `150.4.0` release manifest digests and verify manifests before downloading archives or bindings in packaging and `setup-rusty-v8`, preserving CRLF support.
- Refuse to replace published V8 releases, remove unfinished drafts on retry, and use `gh release create` to upload assets before publication.
- Install Windows `sccache` through a pinned `taiki-e/install-action` in the release and canary workflows.
- Document independent manifest verification and digest recording for version updates.
## Testing
Add five packaging tests covering successful downloads, CRLF manifests, tampered manifests, missing pins, and missing pin files. Rejection tests verify that artifacts are not downloaded.
GitOrigin-RevId: 5c771cdcff376388e124faa4826bf81135d84b50
