Add local Arch package build helper

- packaging/arch/build-local.sh: build a native .pkg.tar.zst from the
  current git HEAD without needing a published forge release (tarballs
  the checkout and runs makepkg --nodeps with the existing PKGBUILD).
- .gitignore: ignore dist/ (local package output).
- sunstone-gtk: drop invalid `margin: 0 auto` on .kind-badge children;
  GTK CSS rejects `auto` for margin, which logged a parse warning. The
  value was already being ignored, so rendering is unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packaging/arch/build-local.sh

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+# Build a native Arch package (.pkg.tar.zst) from the current git HEAD, without
+# needing a published forge release. Uses the same recipe as ./PKGBUILD but
+# sources a tarball of the local checkout instead of downloading from the forge.
+#
+# Usage:  packaging/arch/build-local.sh
+# Output: dist/sunstone-<ver>-<rel>-x86_64.pkg.tar.zst  (in the repo root)
+#
+# Install the result with:  sudo pacman -U dist/sunstone-*.pkg.tar.zst
+set -euo pipefail
+
+repo_root="$(git -C "$(dirname "$0")" rev-parse --show-toplevel)"
+pkgbuild="$repo_root/packaging/arch/PKGBUILD"
+ver="$(awk -F\" '/^version = / {print $2; exit}' "$repo_root/Cargo.toml")"
+
+distdir="$repo_root/dist"
+workdir="$(mktemp -d)"
+trap 'rm -rf "$workdir"' EXIT
+
+echo ">> Packaging sunstone $ver from $(git -C "$repo_root" rev-parse --short HEAD)"
+
+# tracked files only, extracted under sunstone/ to match _srcdir in PKGBUILD.
+git -C "$repo_root" archive --format=tar.gz --prefix="sunstone/" \
+  -o "$workdir/sunstone-$ver.tar.gz" HEAD
+
+# Local PKGBUILD: pin pkgver + swap the forge source for the local tarball.
+sed -e "s|^pkgver=.*|pkgver=$ver|" \
+    -e "s|^source=.*|source=(\"sunstone-\$pkgver.tar.gz\")|" \
+    "$pkgbuild" > "$workdir/PKGBUILD"
+
+# --nodeps: skip makepkg's install-check of runtime deps (gst plugins etc.) —
+# they're declared in the package but needn't be installed on the build host.
+# Build-time libs are checked separately by the compile itself.
+( cd "$workdir" && makepkg -f --nodeps )
+
+mkdir -p "$distdir"
+cp -f "$workdir"/*.pkg.tar.* "$distdir"/
+echo
+echo ">> Built:"
+ls -1 "$distdir"/*.pkg.tar.*