feat(extractors): add GDScript (.gd) + Godot scene/resource (.tscn/.t…

[ozdemirsarman]

Add GDScript + Godot scene/resource extraction

Adds first-class support for Godot Engine projects: GDScript (.gd) AST
extraction plus a grammar-free extractor for Godot's scene/resource/project
text formats (.tscn, .tres, project.godot). This closes the gap where a
Godot codebase currently contributes almost nothing to the graph.

What's new

GDScript (.gd) — graphify/extractors/gdscript.py (tree-sitter-gdscript)

GDScript	Graph
class_name Foo / inner class Foo	class node + defines
extends Bar / extends "res://x.gd"	extends edge (res:// resolved)
func f(): …	function node + defines
foo() / obj.method() in a body	calls edges (local funcs resolved)
Autoload.method()	calls edge resolved to the function in the autoload's script (autoload map read from project.godot)
signal s(args)	signal node + declares
emit_signal("s") / s.emit()	emits edge
s.connect(handler)	connects edge (handler resolved to local func)
preload("res://y.gd") / load(...)	imports edge (res:// resolved)

Godot scenes/resources/project — graphify/extractors/godot_scene.py (no grammar; line parser)

Godot	Graph
[ext_resource type="Script" path="res://x.gd"]	attaches_script edge
[ext_resource type="PackedScene" path="res://y.tscn"]	instances edge
script = ExtResource("id") on a node	node-level attaches_script
[connection signal="s" from="A" to="." method="m"]	connects edge, resolved to the target script's function node
project.godot [autoload]	global singleton node + autoload + script edges
project.godot run/main_scene	main_scene edge

The scene [connection] → function resolution is the payoff Godot devs can't
get from GDScript-only tooling: signal wires defined in .tscn files link
straight to the handler func in the .gd file, because both sides mint the
same _make_id(script_stem, method) node id.

Wiring (mirrors every other language)

• graphify/extractors/gdscript.py, graphify/extractors/godot_scene.py (new)
• detect.py: .gd .tscn .tres .godot added to CODE_EXTENSIONS
• extract.py: facade re-exports + _DISPATCH entries
• extractors/__init__.py: LANGUAGE_EXTRACTORS registry entries
• pyproject.toml: optional godot = ["tree-sitter-gdscript"] extra
• README.md: language table updated

Graceful degradation

Both extractors are safe without the grammar. .gd returns a bare file node
when tree-sitter-gdscript is absent (same pattern as sql/pascal), and the
scene extractor needs no grammar at all — so scene/autoload/signal-wire edges
always work.

Tests

tests/test_gdscript.py (skipped when the grammar is absent) and
tests/test_godot_scene.py (always runs) cover every relation above, plus the
registry-identity sweep in test_extractors_registry.py auto-covers the two new
registry entries. All fixtures are synthetic; no third-party project code.

Open question for maintainers — grammar packaging

tree-sitter-gdscript (PrestonKnopp, MIT) is not yet published to PyPI as a
standalone wheel, though its repo ships working Python bindings and builds from
source cleanly. The .gd loader therefore tries tree_sitter_gdscript first
and falls back to a grammar from tree-sitter-language-pack. I'm happy to (a)
publish tree-sitter-gdscript to PyPI with proper attribution, or (b) switch
the godot extra to whatever dependency you prefer — let me know. The .tscn
half needs no grammar regardless.