feat: Rewrite Python extractor on tree-sitter AST with Django support (#28)

* Enhance Python extractor with Django support and update tests

* Add Python AST extraction and related tests for improved fact generation

* Enhance Python AST extractor for Django support and improve route handling

- Added handling for assignment nodes in the AST to capture Django urlpatterns at the module level.
- Updated the expression statement handler to also process Django urlpatterns.
- Enhanced the decorated definition handler to back-fill route facts with the corresponding handler names.
- Improved dependency tracking by changing the target format in import statements.
- Modified the function handling to distinguish between methods and top-level functions.
- Updated tests to use a unified extraction function and removed redundant file handling code.
- Cleaned up unused helper tests and ensured consistent handling of class and function definitions.

* Fix stale pointer bug in pyWalker and skip @overload stubs

Replace ownerStack/pendingRouteIndices pointer captures with slice indices
to prevent silently lost call edges and handler back-fills when w.out
reallocates its backing array during body traversal.

Skip @overload-decorated function definitions to avoid emitting duplicate
symbol facts for type-checker-only stubs that have no runtime behaviour.

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

* Update tree-sitter-python dependency to v0.23.6 in go.mod and go.sum

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: GertL

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/modelcontextprotocol/go-sdk v1.3.0
 	github.com/tree-sitter-grammars/tree-sitter-kotlin v1.1.0
 	github.com/tree-sitter/go-tree-sitter v0.24.0
+	github.com/tree-sitter/tree-sitter-python v0.23.6
 	github.com/tree-sitter/tree-sitter-typescript v0.23.2
 	gopkg.in/yaml.v3 v3.0.1
 )

go.sum

@@ -36,8 +36,8 @@ github.com/tree-sitter/tree-sitter-json v0.21.1-0.20240818005659-bdd69eb8c8a5 h1
 github.com/tree-sitter/tree-sitter-json v0.21.1-0.20240818005659-bdd69eb8c8a5/go.mod h1:GbMKRjLfk0H+PI7nLi1Sx5lHf5wCpLz9al8tQYSxpEk=
 github.com/tree-sitter/tree-sitter-php v0.22.9-0.20240819002312-a552625b56c1 h1:ZXZMDwE+IhUtGug4Brv6NjJWUU3rfkZBKpemf6RY8/g=
 github.com/tree-sitter/tree-sitter-php v0.22.9-0.20240819002312-a552625b56c1/go.mod h1:UKCLuYnJ312Mei+3cyTmGOHzn0YAnaPRECgJmHtzrqs=
-github.com/tree-sitter/tree-sitter-python v0.21.1-0.20240818005537-55a9b8a4fbfb h1:EXEM82lFM7JjJb6qiKZXkpIDaCcbV2obNn82ghwj9lw=
-github.com/tree-sitter/tree-sitter-python v0.21.1-0.20240818005537-55a9b8a4fbfb/go.mod h1:lXCF1nGG5Dr4J3BTS0ObN4xJCCICiSu/b+Xe/VqMV7g=
+github.com/tree-sitter/tree-sitter-python v0.23.6 h1:qHnWFR5WhtMQpxBZRwiaU5Hk/29vGju6CVtmvu5Haas=
+github.com/tree-sitter/tree-sitter-python v0.23.6/go.mod h1:cpdthSy/Yoa28aJFBscFHlGiU+cnSiSh1kuDVtI8YeM=
 github.com/tree-sitter/tree-sitter-ruby v0.21.1-0.20240818211811-7dbc1e2d0e2d h1:fcYCvoXdcP1uRQYXqJHRy6Hec+uKScQdKVtMwK9JeCI=
 github.com/tree-sitter/tree-sitter-ruby v0.21.1-0.20240818211811-7dbc1e2d0e2d/go.mod h1:T1nShQ4v5AJtozZ8YyAS4uzUtDAJj/iv4YfwXSbUHzg=
 github.com/tree-sitter/tree-sitter-rust v0.21.3-0.20240818005432-2b43eafe6447 h1:o9alBu1J/WjrcTKEthYtXmdkDc5OVXD+PqlvnEZ0Lzc=