Add shared runtime build information (#37929)

## What changed

- Add `codex-build-info` to resolve a packaged runtime's semantic version from `codex-package.json` while preserving the commit stamped into the executable.
- Represent source builds as version `0.0.0` and expose helpers for display, serialization, and source-build detection.
- Stamp `STABLE_GIT_COMMIT` into final Bazel Rust binaries so Git changes do not invalidate the shared library graph.

## Testing

- Cover packaged, source, legacy, and invalid-version resolution, plus serialization round trips.

GitOrigin-RevId: 669b02449644c738ba2946a1b7aafe4ec31a9edb

codex-rs/build-info/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+edition.workspace = true
+license.workspace = true
+name = "codex-build-info"
+version.workspace = true
+
+[lib]
+doctest = false
+name = "codex_build_info"
+path = "src/lib.rs"
+
+[lints]
+workspace = true
+
+[dependencies]
+codex-install-context = { workspace = true }
+semver = { workspace = true, features = ["serde"] }
+serde = { workspace = true, features = ["derive"] }
+
+[dev-dependencies]
+pretty_assertions = { workspace = true }
+serde_json = { workspace = true }
+tempfile = { workspace = true }