Add md2pdf: Markdown-to-PDF CLI with Finder Quick Action

- bin/md2pdf: converts .md to PDF via pandoc + headless Chrome
  (no LaTeX needed); writes alongside source, supports -o and --css
- bin/md2pdf.css: clean GitHub-style default stylesheet
- bin/md2pdf-install-quickaction: installs the Finder right-click action
- macos/md2pdf.workflow: version-controlled Quick Action bundle
  (right-click .md files to Convert to PDF)

bin/md2pdf-install-quickaction

@@ -0,0 +1,65 @@
+#!/bin/zsh
+#
+# md2pdf-install-quickaction — install (or refresh) the "Convert to PDF"
+# Finder Quick Action.
+#
+# Symlinks the version-controlled workflow bundle from the dotfiles repo into
+# ~/Library/Services so edits in the repo take effect without reinstalling,
+# then flushes the Services cache so the menu item appears immediately.
+#
+# Usage: md2pdf-install-quickaction [--copy]
+#   --copy   Install a copy instead of a symlink (use if you prefer the
+#            installed action to be independent of the repo).
+
+emulate -L zsh
+set -o pipefail
+
+prog=${0:t}
+die() { print -u2 "$prog: $*"; exit 1; }
+
+local mode=symlink
+[[ $1 == --copy ]] && mode=copy
+[[ -n $1 && $1 != --copy ]] && die "unknown argument: $1 (only --copy is supported)"
+
+# Source bundle lives next to this script: ../macos/md2pdf.workflow
+local src="${0:A:h:h}/macos/md2pdf.workflow"
+[[ -d $src ]] || die "workflow bundle not found at $src"
+
+local services="$HOME/Library/Services"
+local dest="$services/md2pdf.workflow"
+
+mkdir -p "$services" || die "could not create $services"
+
+# Remove any prior install (symlink or directory) so we start clean.
+if [[ -L $dest || -e $dest ]]; then
+  rm -rf -- "$dest" || die "could not remove existing $dest"
+fi
+
+if [[ $mode == symlink ]]; then
+  ln -s "$src" "$dest" || die "could not symlink workflow into $services"
+  print -- "✓ linked $dest -> $src"
+else
+  cp -R "$src" "$dest" || die "could not copy workflow into $services"
+  print -- "✓ copied workflow to $dest"
+fi
+
+# Refresh the Services/Quick Actions registry so the item shows up now.
+local pbs="/System/Library/CoreServices/pbs"
+if [[ -x $pbs ]]; then
+  "$pbs" -flush 2>/dev/null
+  print -- "✓ flushed Services cache"
+fi
+# Nudge the Extensions/Quick Actions registration too (harmless if absent).
+/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister \
+  -f "$dest" 2>/dev/null
+
+cat <<EOF
+
+Installed. To use it:
+  • In Finder, right-click one or more .md files
+  • Choose  Quick Actions ▸ Convert to PDF (md2pdf)   (may be under a "..." submenu)
+
+If it doesn't appear immediately, toggle it on in:
+  System Settings ▸ Keyboard ▸ Keyboard Shortcuts… ▸ Services ▸ Files and Folders
+(or log out and back in to fully refresh the Services menu).
+EOF