Add fat Ubuntu 26.04 base image with runit, Go, Node, Python toolchains

Single-RUN image built by build.sh on ubuntu:26.04: build-essential,
distro plus latest Go, nvm with Node LTS, corepack with yarn/pnpm cached,
wrangler, hugo extended, golangci-lint, pyenv with latest Python 3, pip
and virtualenv. runit services supervised under runsvinit as PID 1.
Docs, man pages, caches and non-English locales stripped.

Includes build logs for the 2026-11-05 release (amd64 and arm64).

rootfs/etc/dpkg/dpkg.cfg.d/01_nodoc

@@ -0,0 +1,10 @@
+# Keep documentation and non-English locales out of the image. Applies to
+# every package installed here and in child images.
+path-exclude /usr/share/doc/*
+path-include /usr/share/doc/*/copyright
+path-exclude /usr/share/man/*
+path-exclude /usr/share/info/*
+path-exclude /usr/share/lintian/*
+path-exclude /usr/share/locale/*
+path-include /usr/share/locale/en*
+path-include /usr/share/locale/locale.alias

rootfs/etc/profile.d/baseimage.sh

@@ -0,0 +1,8 @@
+# Interactive shells get the nvm and pyenv shell functions. Non-interactive
+# use does not need this: the image's PATH already points at the installed
+# toolchains.
+export NVM_DIR="${NVM_DIR:-/usr/local/nvm}"
+[ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh" --no-use
+
+export PYENV_ROOT="${PYENV_ROOT:-/usr/local/pyenv}"
+command -v pyenv >/dev/null 2>&1 && eval "$(pyenv init - --no-rehash)"