dotcli: Add dot kde save with schema-backed defaults and completion.

Introduces the dot kde subcommand family (fish dispatcher plus a Python
helper under commands/kde/), a flat identifier=value manifest, and
dot kde save in both its explicit-identifier and no-argument refresh
modes. Settings resolve to KDE's KConfigXT schema-backed mechanism via a
(rcfile -> [kcfg files]) mapping table auto-derived by scanning the
system schema directory (overridable via DOT_KDE_KCFG_DIR), plus a
hand-maintained exceptions list for schemas that only declare their
target rc file at runtime. Also wires tab-completion for dot kde save
identifiers, sourced live from that same mapping table.

.config/dot/commands/kde/kde.fish

@@ -0,0 +1,27 @@
+function _dot_kde_usage
+    echo "usage: dot kde <command>
+
+Commands:
+  save    write live KDE settings into the manifest
+  help    show this message
+
+Run 'dot kde <command> help' for flags on a specific command."
+end
+
+function _dot_kde
+    if test "$argv[1]" = help
+        _dot_kde_usage
+        return 0
+    end
+
+    set -l helper_dir (status dirname)
+
+    switch "$argv[1]"
+        case save
+            python3 $helper_dir/kde.py save $argv[2..-1]
+            return $status
+        case '*'
+            _dot_kde_usage
+            return 1
+    end
+end