/add-unit -- Add a New Course Unit

Add a new unit to the Writer Course curriculum.

Required inputs (ask user if not provided)

• •Unit title
• •Start page and end page in the PDF
• •3 learning objectives (actionable, starting with a verb)

Steps

1. •Determine the next sequential unit ID by reading src/unit_catalog.py and finding the last entry in RAW_UNITS
2. •Add a new dict entry to RAW_UNITS in src/unit_catalog.py, matching the existing format:
   python

   {
       "id": "<next_id>",
       "title": "<title>",
       "start_page": <start>,
       "end_page": <end>,
       "learning_objectives": [
           "<obj1>",
           "<obj2>",
           "<obj3>",
       ],
   },
   

3. •Delete data/units.json and data/exercises.json so caches rebuild on next app launch
4. •Run pytest tests/test_units.py -v to verify the unit map still loads correctly
5. •Confirm: the chunk cache (data/chunks.json) will rebuild automatically on next streamlit run

Invariants to maintain

• •Unit IDs must be sequential string integers ("0", "1", "2", ...)
• •Page ranges must not overlap with existing units
• •Each unit must have exactly 3 learning objectives
• •Learning objectives must be actionable (start with a verb)