Constant KERNEL_HELP_BUILD 

pub const KERNEL_HELP_BUILD: &str = "Kernel to build: a version (`6.14.2`, \
     a `MAJOR.MINOR` prefix `6.14` for the latest patch in that series, or a \
     bare `MAJOR` prefix `6` for the latest patch across all `6.x`), a version range \
     (`6.11..6.14` — builds every stable/longterm release in the range), a \
     source directory path (`./linux`, `~/linux`, or an absolute path; a \
     bare relative name like `linux` is read as a cache key, so prefix a \
     relative source dir with `./`), or a git source (`git+URL#tag=NAME`, \
     `git+URL#branch=NAME`, or `git+URL#sha=<40-hex>`). Omitted, the latest \
     stable release is built. A cache key (an already-built entry from \
     `kernel list`) is rejected — it names a built kernel, so there is \
     nothing to build. Build one kernel (or one range) per invocation.";

Help text for --kernel on kernel build (ktstr and cargo ktstr). Unlike KERNEL_HELP_NO_RAW, this surface builds a kernel rather than resolving one for a test run: it is NOT repeatable (one kernel or one range per invocation), and a cache key is rejected (a cache key names an already-built entry, so there is nothing to build). A source-directory path auto-builds; a version / range auto-downloads; a git source is fetched and built. Omitting --kernel builds the latest stable release.