fix(pkg-py): Standardize categorical_threshold default to 20 (#125)

Updates the Python package to use categorical_threshold=20 as the default
value, matching the R package default. This resolves the inconsistency
between the two implementations.

Fixes #122

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <[email protected]>

Author: cpsievert

pkg-py/src/querychat/_deprecated.py

@@ -77,7 +77,7 @@ def system_prompt(
     *,
     data_description: Optional[str | Path] = None,
     extra_instructions: Optional[str | Path] = None,
-    categorical_threshold: int = 10,
+    categorical_threshold: int = 20,
     prompt_template: Optional[str | Path] = None,
 ) -> str:
     """

pkg-py/src/querychat/_querychat.py

@@ -34,7 +34,7 @@ def __init__(
         greeting: Optional[str | Path] = None,
         client: Optional[str | chatlas.Chat] = None,
         data_description: Optional[str | Path] = None,
-        categorical_threshold: int = 10,
+        categorical_threshold: int = 20,
         extra_instructions: Optional[str | Path] = None,
         prompt_template: Optional[str | Path] = None,
     ):
@@ -532,7 +532,7 @@ def __init__(
         greeting: Optional[str | Path] = None,
         client: Optional[str | chatlas.Chat] = None,
         data_description: Optional[str | Path] = None,
-        categorical_threshold: int = 10,
+        categorical_threshold: int = 20,
         extra_instructions: Optional[str | Path] = None,
         prompt_template: Optional[str | Path] = None,
         enable_bookmarking: Literal["auto", True, False] = "auto",
@@ -697,7 +697,7 @@ def get_system_prompt(
     *,
     data_description: Optional[str | Path] = None,
     extra_instructions: Optional[str | Path] = None,
-    categorical_threshold: int = 10,
+    categorical_threshold: int = 20,
     prompt_template: Optional[str | Path] = None,
 ) -> str:
     # Read the prompt file