script/build stamps lightweight tags too (closes #156)

When VERSION is unset or empty, script/build now takes the version from
`git describe --tags --always --dirty`, the form script/docker and
script/cibuild use. Without --tags it ignored lightweight tags, so a
binary from `make build` could report a commit where the image built
from the same tree reported the tag. README.md Entrypoints names the
same form.

Model: opus-5-5

TODO.md

@@ -22,6 +22,12 @@ Run `make frontend-viewport-test` in CI as its own step; it is not part of
 
 # Completed Steps
 
+- 2026-10-19: when `VERSION` is unset or empty, `script/build` stamps the
+  version from `git describe --tags --always --dirty`, as `script/docker` does
+  ([#156](https://git.eeqj.de/sneak/netwatch/issues/156)). Without `--tags` it
+  skipped lightweight tags, so `make run` could report a commit where the image
+  built from the same tree reported the tag. Checked once with a lightweight tag
+  on a scratch clone: `make build` stamped it
 - 2026-10-19: `.dockerignore` keeps Go test binaries and coverage output at the
   root out of the build context, with `/*.test` and `/*.out` in the repository's
   own section ([#155](https://git.eeqj.de/sneak/netwatch/issues/155)). Such