feat: Add template spell picker from spells.yml; polish spell table

- Add yaml-loader; import data/spells.yml at build time
- Add SpellTemplate/SpellsFile types to globals.d.ts
- Add 'Add Template Spell' button that opens a modal picker pre-filling
  all spell fields from the YAML data
- Move spell data files into data/ directory
- Split spell rows into inputs row + full-width notes row (colspan=6)
- Shrink delete column to fit-content; bold spell name input
- Add class column to spell table; change MP cost to free-text input
- Auto-resize spell notes textarea on load and on input
- Add 10px padding between spells for visual separation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/anchors.py

@@ -0,0 +1,69 @@
+# /// script
+# requires-python = ">=3.12"
+# dependencies = [
+#     "bs4",
+# ]
+# ///
+
+
+from bs4 import BeautifulSoup
+import re
+from pathlib import Path
+
+# Dictionary to track how many times we've seen each header ID
+header_seen = {}
+
+def add_anchors_to_headers(html_content):
+    # Parse the HTML content
+    soup = BeautifulSoup(html_content, 'html.parser')
+    
+    # Find all header tags (h1 through h6)
+    header_tags = soup.find_all(['h1', 'h2', 'h3', 'h4', 'h5', 'h6'])
+    
+    # Add a count-based ID to each header tag
+    for header in header_tags:
+        # Extract header text (fallback to tag name if empty)
+        header_text = header.get_text(strip=True) or header.name
+
+        # Normalize header
+        header_text = header_text.lower().replace(" ", "-")
+
+        # Create base ID: hN-<text>
+        base_id = f"{header.name}-{header_text}"
+
+        # Check if we've seen this base ID before
+        if base_id in header_seen:
+            # Append next count: -1, -2, -3...
+            count = header_seen[base_id]
+            header_seen[base_id] = count + 1
+            header_id = f"{base_id}-{count + 1}"
+        else:
+            # First time seeing this text → count starts at 1
+            header_seen[base_id] = 1
+            header_id = base_id
+
+        # Add the ID to the header tag
+        header['id'] = header_id
+
+        # Wrap the header in an anchor link (clickable permalink)
+        # The link points to itself via the id attribute
+        # anchor_tag = soup.new_tag("a", href=f"#{header_id}", class_="anchor-link")
+        # anchor_tag.string = f"🔗"
+        # header.wrap(anchor_tag)
+
+    # Return the modified HTML content
+    return str(soup)
+
+for book in ('./books/core', './books/natural-fantasy-atlas'):
+    for root, dirs, files in Path(book).walk():
+        for fn in files:
+            path = root / fn
+            if path.suffix != ".html":
+                continue
+            with path.open('r') as fh:
+                raw_html = fh.read()
+
+            new_html = add_anchors_to_headers(raw_html)
+
+            with path.open('w') as fh:
+                fh.write(new_html)