Expand deck to 42 slides, add speaker notes, and fix editor artifacts

Adds Grounding, Reasoning-Modelle, Token/Parameter examples, an
autocomplete mini-game, and a Copilot agent-building walkthrough with
a live chat-demo payoff. Adds Sprecher.md with per-slide speaker
cards. Fixes malformed data-def attributes and stray baked-in
active/visible classes left over from in-browser edit-mode sessions,
and stops the local save-in-place backups from being tracked.

config.html

@@ -156,7 +156,13 @@
         groups[groupIndex[key]].slides.push(slide);
     });
 
+    const maxId = SLIDE_MANIFEST.length;
     let enabled = loadSlideConfig();
+    // Veraltete Auswahl von einem Deck-Stand mit anderer Slide-Zahl verwerfen
+    // (die letzte Slide ist immer `locked` und muss daher immer enthalten sein).
+    if (enabled && !enabled.has(maxId)) {
+        enabled = null;
+    }
     if (!enabled) {
         enabled = new Set(SLIDE_MANIFEST.map((s) => s.id));
     }