chore: added extract_characters method for detailed character analysis

### CHANGES

- Add `extract_characters` to identify and describe characters
- Update business category to include `extract_characters`
- Include `extract_characters` in extract category
- Add `extract_characters` description in pattern descriptions JSON
- Update user documentation with `extract_characters` details

web/static/data/pattern_descriptions.json

@@ -1878,6 +1878,14 @@
         "ANALYSIS",
         "WRITING"
       ]
+    },
+    {
+      "patternName": "extract_characters",
+      "description": "Identify all characters (human and non-human), resolve their aliases and pronouns into canonical names, and produce detailed descriptions of each character's role, motivations, and interactions ranked by narrative importance.",
+      "tags": [
+        "ANALYSIS",
+        "WRITING"
+      ]
     }
   ]
 }