fix(dart): resolve chained static-factory / constructor calls Foo.create().bar() (#750) (#762)

Ports the #645/#608 chained-receiver mechanism to Dart, plus makes Dart factory
and named constructors first-class so their chains can resolve at all. A call
whose receiver is itself a call — `Foo.create().bar()` (static factory or
factory/named constructor) — used to drop the receiver to a bare `bar`, which
name-matched a same-named method on an unrelated type (commonly a stdlib
`Option`/`Iterator` `.map`/`.where` mis-tied to the project's own class).

- dart.ts: extractBareCall now re-encodes `Foo.create().bar` when the chain
  starts with a capitalized type; getReturnType captures the return type (generic
  `List<Foo>` → `List`); factory (`factory Foo.create()`) and named (`Foo._()`)
  constructors are indexed as `Foo::create` / `Foo::_` with return type = the
  class (via resolveName + getReturnType + constructor_signature in methodTypes).
- The UNNAMED ctor `Foo()` is deliberately NOT extracted (isMisparsedFunction),
  so plain construction stays an `instantiates` edge to the class rather than a
  call to a phantom `Foo::Foo` method.
- dartCtorInfo validates a "constructor" against the enclosing class name, so a
  method tree-sitter MISPARSES as a constructor — `@override (A, B) m()`, where
  the annotation swallows the record return type and `m()` looks like a one-id
  constructor_signature — is still extracted as the method it is (regression
  found on localsend; covered by a new test).
- name-matcher.ts / index.ts: `dart` joins the dotted-chain gate,
  CONSTRUCTS_VIA_BARE_CALL (case construction), and CHAIN_LANGUAGES (conformance
  for superclass/mixin methods). resolveMethodOnType validates, so a wrong
  inference yields no edge.

Validation: 7 synthetic tests (static factory, factory/named ctor, construction,
conformance, absent-method safety, the misparse regression, instantiation-not-
hijacked). Real-repo A/B on localsend (368 Dart files): hand-written +17/-10 — all
corrections (the -10 = 7 wrong stdlib/extension misattributions removed + 3 ctor
source-renames), plus additive factory/named-ctor call resolution. Instantiation
preserved; no node explosion. EXTRACTION_VERSION 13->14. Full suite green.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/extraction/extraction-version.ts

@@ -21,4 +21,4 @@
  * turns the re-index hint into noise — keep it honest (see CLAUDE.md, "Honesty
  * in the product is load-bearing").
  */
-export const EXTRACTION_VERSION = 13;
+export const EXTRACTION_VERSION = 14;