fix: Dart extractor cleanup

[Overman775]

What changed

This PR makes Dart extraction stricter about parser noise. It keeps the current regex-based approach, but avoids creating graph nodes from syntax fragments that are not project entities.

The patch covers a few cases that showed up in real Flutter code:

• part of 'package:...' files now resolve through pubspec.yaml to the parent file under lib/
• generated/private names like _ and _$Foo no longer become graph nodes
• getters and modifiers like String get, bool get, static const, static final are filtered out
• function types, records, constructor params, and factory params no longer create comma-split labels
• common Dart SDK types such as FutureOr, Never, MapEntry, Iterator, Comparable, StackTrace, Exception are filtered from noisy type references
• SDK targets from extension on String/List/Map/Set/Iterable/Future/Stream and SDK typedef targets are filtered as noise
• SDK Iterable<T> from an extension type implements clause is filtered as noise
• Dart 3 syntax is covered: records, patterns, class modifiers, extension types, enhanced enums, wildcard _
• Dart with MyMixin still emits mixes_in

This is not a Dart analyzer rewrite. It only removes false positives that showed up in real projects.

The SDK filter is intentionally conservative. It covers common dart:core and dart:async noise, but does not try to mirror the full Dart SDK. Graphify filters by short name here, so a very broad SDK list could hide project classes with the same names.

Why

The old extractor sometimes treated syntax fragments as project entities. On a real Flutter monorepo I saw nodes like:

_
String get
bool get
static const
String sku, int
mocks_mock_webview_platform_mock

Those nodes are not useful graph facts. They make traversal noisier because they look like real classes, methods, or types.

Real project check

I also ran the extractor against a Flutter monorepo with 1552 Dart files. Extraction errors stayed at 0.

Noise comparison:

item	before	after
_ labels	211	0
String get labels	114	0
bool get labels	39	0
static const/final labels	49	0
comma-label nodes	49	0
fake file-scoped Mock node	1	0
SDK String/List/Map/Iterable/Future labels	119	0

Most structural relations stayed stable:

relation	before	after
imports	6066	6066
exports	364	364
inherits	687	687
calls	351	351
navigates	40	40
extends	283	265
implements	580	579

The two drops are intentional. extends drops because SDK targets from ordinary Dart extensions are now filtered; project extension targets still remain. implements drops because one SDK Iterable<T> edge from an extension type is now filtered.

Migration note

If you already have a graph for a Dart or Flutter project, run a forced rebuild once after updating:

graphify . --force

Older graphify-out/graph.json files may already contain the parser-noise nodes removed here. A forced rebuild removes those stale nodes instead of carrying them through an incremental update.

Notes

The new tests focus on regression cases, not every Dart grammar rule. They cover the bugs above plus Dart 3 syntax that previously had a good chance of creating fake graph nodes.

[Overman775]

@safishamsi Hi! Please take a look at the PR )