chore: add cargo-deny configuration (#7119)

- add GitHub workflow running cargo-deny on push/PR
- document cargo-deny allowlist with workspace-dep notes and advisory
ignores
- align workspace crates to inherit version/edition/license for
consistent checks

codex-rs/utils/readiness/Cargo.toml

@@ -2,6 +2,7 @@
 name = "codex-utils-readiness"
 version.workspace = true
 edition.workspace = true
+license.workspace = true
 
 [dependencies]
 async-trait = { workspace = true }