refactor: group stow packages into common, mac and kde

Split the packages by platform so each app stays an opt-in Stow package
under common/, mac/ or kde/. KDE gets its own Fastfetch, Helium and
Spectacle packages, and darwin-breeze becomes kde/theme. The READMEs
document stowing a whole group as well as individual packages.

kde/spectacle/apply.py

@@ -0,0 +1,85 @@
+#!/usr/bin/env python3
+"""Apply screenshot preferences and reload Spectacle's KDE shortcuts."""
+
+import ast
+import configparser
+import os
+from pathlib import Path
+import re
+import subprocess
+
+
+HERE = Path(__file__).resolve().parent
+COMPONENT = "org.kde.spectacle.desktop"
+ACCEL = "/component/org_kde_spectacle_desktop"
+
+
+def run(*args, **kwargs):
+    return subprocess.run(args, check=True, text=True, **kwargs)
+
+
+def accel(path, method, *args):
+    return run(
+        "gdbus", "call", "--session", "--dest", "org.kde.kglobalaccel",
+        "--object-path", path, "--method", method, *args,
+        capture_output=True,
+    ).stdout
+
+
+def main():
+    for name in ("spectaclerc", "klipperrc"):
+        config = configparser.ConfigParser(interpolation=None)
+        config.optionxform = str
+        config.read(HERE / "settings" / name)
+        for group in config.sections():
+            for key, value in config[group].items():
+                run("kwriteconfig6", "--file", name, "--group", group,
+                    "--key", key, value)
+
+    # T3's locale and XDG_DATA_DIRS can differ from the running KDE session.
+    # Build the cache KDE actually reads, rather than an app-specific cache.
+    session = dict(
+        line.split("=", 1) for line in
+        run("systemctl", "--user", "show-environment", capture_output=True)
+        .stdout.splitlines() if "=" in line
+    )
+    env = os.environ.copy()
+    for key in ("LANG", "LANGUAGE", "XDG_DATA_DIRS", "XDG_DATA_HOME",
+                "XDG_CACHE_HOME", "XDG_CONFIG_HOME"):
+        env.pop(key, None)
+        if key in session:
+            env[key] = session[key]
+    for key in set(env) | set(session):
+        if key.startswith("LC_"):
+            env.pop(key, None)
+            if key in session:
+                env[key] = session[key]
+    run("kbuildsycoca6", "--noincremental", env=env)
+
+    # Existing shortcut components retain their old Exec commands. Recreate
+    # only Spectacle's component, preserving any customized key bindings.
+    try:
+        output = accel(ACCEL, "org.kde.kglobalaccel.Component.allShortcutInfos")
+    except subprocess.CalledProcessError:
+        shortcuts = []  # Component has not been registered yet.
+    else:
+        shortcuts = ast.literal_eval(re.sub(r"@a[is] ", "", output))[0]
+        accel(ACCEL, "org.kde.kglobalaccel.Component.cleanUp")
+
+    action = [COMPONENT, "_reload_config", "Spectacle", "Reload configuration"]
+    accel("/kglobalaccel", "org.kde.KGlobalAccel.doRegister", repr(action))
+    accel("/kglobalaccel", "org.kde.KGlobalAccel.unregister",
+          COMPONENT, "_reload_config")
+    for name, label, component, friendly, context, _, keys, defaults in shortcuts:
+        if keys != defaults:
+            identity = component if context == "default" else f"{component}|{context}"
+            accel("/kglobalaccel", "org.kde.KGlobalAccel.setForeignShortcut",
+                  repr([identity, name, friendly, label]), repr(keys))
+
+    run("qdbus6", "org.kde.klipper", "/klipper",
+        "org.kde.klipper.klipper.reloadConfig")
+    print("Applied Spectacle: copy to clipboard with a notification, no preview.")
+
+
+if __name__ == "__main__":
+    main()