## Why
CI jobs repeat common bootstrap steps, which makes it harder to keep
Bazel and Cargo lanes aligned. Centralizing the lightweight setup gives
us one place for future runner-wide optimizations without adding Rust
toolchain or component installation to the Windows Bazel long poles.
## What
- add zero-input `.github/actions/setup-ci` to set Cargo's git
transport, install DotSlash and `just`, expose DotSlash from stable PATH
locations, and enable Windows Git long paths
- have `setup-bazel-ci` compose the common setup, then remove its
DotSlash/test-prerequisite plumbing
- migrate Bazel, Cargo CI, V8 canary, repo checks, nextest, and Windows
release call sites while keeping Rust toolchain and MSVC setup explicit
- preserve the existing nextest Dev Drive setup unchanged
## Validation
- `just test-github-scripts` (30 tests)
- parsed workflow and composite-action YAML with `yq`
Avoid rebuilding sandboxed Windows MSVC V8 artifacts for unrelated
changes to `codex-rs/Cargo.toml`.
The V8 canary now compares the resolved V8 version between the base and
head commits and only runs the Windows source-build matrix when:
- the resolved V8 crate version changes;
- Windows artifact-production scripts or workflows change; or
- the workflow is manually dispatched.
The existing Bazel V8 matrix is unchanged.
## Why
The Windows MSVC source builds take roughly two to three hours and
currently run whenever any entry in the broad `v8-canary` path filter
changes.
