fix: extract INHERITS edges for Go, Kotlin, Swift, Dart, Objective-C

[pradeepmouli]

Summary

Follow-up to #21 (TypeScript/Rust INHERITS extraction). Same class of
gap in five more mainstream languages -- none captured any
inheritance-like relationship at all:

• go: struct embedding (Go's closest analog to inheritance -- an
  anonymous field with no name, just a type). Interface satisfaction is
  implicit/structural in Go and can't be determined from syntax alone, so
  it's intentionally not covered.
• kotlin: class inheritance and interface implementation via
  delegation_specifiers (class X : Y() / class X : Y).
• swift: class/struct/enum inheritance and protocol conformance
  (class X: Y, protocol X: Y).
• dart: extends and implements.
• objc: class inheritance (@interface X : Y). Also fixes a separate,
  deeper bug in objc/entities.scm: class_interface,
  class_implementation, and protocol_declaration all used a name:
  field that doesn't exist on those grammar nodes (confirmed against
  tree-sitter-objc's node-types.json -- the class name is an unlabeled
  positional child, not a field), so every Objective-C class/protocol
  produced zero symbols at all, not just zero inheritance edges.
  Without fixing that too, the new relations.scm pattern would have
  nothing to bind to.

Fix

Verified every grammar's exact node structure against the vendored
tree-sitter-* node-types.json (and, for Objective-C, the compiled
grammar.json for positional/unlabeled child structure) rather than
guessing.

Test plan

• Compiles clean, no language-pack load warnings for any of the five
• Full infigraph-core (268) and infigraph-languages (16) test
  suites pass
• Five new regression tests in
  infigraph-languages/tests/registry_integration.rs, one per
  language (the Objective-C test also asserts symbols are extracted,
  covering the entities.scm fix)
• End-to-end against synthetic files covering each pattern -- all
  five produce correct INHERITS edges (Objective-C additionally
  confirmed to now produce symbols where it previously produced zero)

🤖 Generated with Claude Code

https://claude.ai/code/session_01TAXDJyFdnA4BV1U2fxufdC

[johnintuit]

Same issue like PR#21 - Kindly check here also @pradeepmouli

crates/infigraph-languages/languages/go/relations.scm, embedded-field query (type: (type_identifier)):
🔴 bug: field_declaration.type field allows qualified_type (cross-package embed) and generic_type too, per grammar. type Dog struct { pkg.Animal } — very common Go pattern — parses as qualified_type, not type_identifier. Edge silently dropped. Fix: type: (_) @inherit.parent. Add test for package-qualified embedding.

crates/infigraph-languages/languages/dart/relations.scm, L28 and L35 ((type_identifier) inside superclass/interfaces):
🔴 bug: Dart's _type_not_void grammar rule (used by both extends/implements) wraps the type name plus optional type_arguments, and the type name itself can be library-prefixed (pkg.Animal). class Dog extends Animal<T> or extends pkg.Animal won't match a bare type_identifier child. Fix: (type_identifier) → (_) @inherit.parent, or match on the type node directly without descending into a specific child type. Add tests for generic and prefixed base classes.