rebuild dev and build system with single marp server

- simplify development: single marp server on port 3000 instead of 3 processes
- rename klausur to klausurfolien for better naming
- update extract script to use 00-intro.md as template when no 01-*.md exists
- update makefile and package.json for new workflow
- add comprehensive AGENTS.md guidelines

package.json

@@ -3,13 +3,14 @@
   "version": "1.0.0",
   "description": "HdM Stuttgart - Lecture Slides (Marp)",
   "scripts": {
-    "dev:b": "PORT=1312 marp --server --allow-local-files courses/223015b/slides/",
-    "dev:c": "PORT=1313 marp --server --allow-local-files courses/223015c/slides/",
+    "dev": "PORT=3000 marp --server --allow-local-files slides/",
     "build": "make build",
     "build:b": "make build-b",
     "build:c": "make build-c",
     "pdf": "make pdf",
     "html": "make html",
+    "klausur": "make klausur",
+    "deploy": "make deploy",
     "test": "echo \"No tests specified\" && exit 0"
   },
   "keywords": ["marp", "slides", "hdm", "lectures"],