Add theme-set/switching logic, and minor nvim, tmux, obsidian changes

src_files/.local/scripts/theme-update-wallpaper

@@ -0,0 +1,26 @@
+#!/bin/zsh
+
+
+set_wallpaper_linux() {
+    echo "TODO: theme_update_wallpaper_linux not yet implemented"
+}
+
+set_wallpaper_macos() {
+    # after back and forth with gpt and failing approaches, landing on this swift snippet
+    swift <(cat << NESTED_SWIFT_BLOCK
+        import AppKit
+        let url = URL(fileURLWithPath: "$1")
+        try NSWorkspace.shared.setDesktopImageURL(url, for: NSScreen.main!, options: [:])
+NESTED_SWIFT_BLOCK
+    )
+}
+
+# TODO: decide if and how to make this work for cycling through wallpapers per theme
+
+wallpaper_dir=$DIR_THEME_SETTINGS/.current-theme/wallpaper
+image_paths=($(find $wallpaper_dir -type f | sort)) 2> /dev/null
+target_wallpaper=${image_paths[@]:0:1}
+[[ -z $target_wallpaper ]] && exit 0
+
+[[ "$OSTYPE" = *"darwin"* ]] && set_wallpaper_macos $target_wallpaper ||
+    set_wallpaper_linux $target_wallpaper