Give development builds their own Debian package version

make deb versions a build that isn't a release after the last tag:
0.2.0~rc.1+git3.gca0f148, plus the build time (.m<UTC time>) with
uncommitted changes. apt sorts it after that RC and before the next, so
installing it over the RC or an older build is an upgrade and needs no
--reinstall. mkdeb.sh removes older packages of the same architecture
from dist/ so the install globs match one package.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/development.md

@@ -252,6 +252,15 @@ it on Gitea). Only a release build reports a version number:
 
 `RELEASE_TAG=v0.2.0 make` forces the first case.
 
+`make deb` versions the packages the same way. A release gets `VERSION`
+with `~` for `-` (`0.2.0~rc.1`). A development build gets a version after
+the last tag: 3 commits past `v0.2.0-rc.1` is `0.2.0~rc.1+git3.gca0f148`,
+and uncommitted changes add the build time (`.m20261009153000`). apt sorts
+these after that RC and before the next one or `0.2.0`. So installing a
+newer build over an older one, or over the RC, is an upgrade: plain
+`apt install ./dist/…` works, without `--reinstall`. `make deb` removes
+older packages of the same architecture from `dist/` first.
+
 Pushing the same tag again (`git tag -f`, `git push -f`) re-runs it, and
 the script replaces the attachments and packages, so a failed release can
 simply be retried.