Add registry-backed language extraction

[andrew]

Extends the structured Imports and Refs APIs from #28 to Dart, Swift, Haskell, Perl, Lua, R, Julia, OCaml, Crystal, Nim, Zig, and D.

Covers module aliases, selected imports, side-effect forms, and each language's qualified member access.

Depends on #28.

[Copilot]

Pull request overview

Extends the existing structured Imports and Refs extraction APIs to support additional languages by adding registry-backed import/reference extractors and wiring them into the existing dispatch logic.

Changes:

• Adds language-specific import extraction for Dart, Swift, Haskell, Perl, Lua, R, Julia, OCaml, Crystal, Nim, Zig, and D.
• Adds language-specific reference extraction for the same set (plus some via shared member-access helpers).
• Adds test coverage for the new registry-backed import/ref extractors and updates README language coverage.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
ref.go	Adds new language cases for Refs and generalizes member-ref extraction via memberRefsWithFields.
ref_registry.go	Implements registry-backed reference extraction for Dart, Swift, Haskell, OCaml, and D.
ref_registry_test.go	Adds tests validating Refs behavior for the newly supported languages.
import.go	Adds new language cases for Imports and introduces shared importStatement constant.
import_registry.go	Implements registry-backed import extraction for Dart, Swift, Haskell, Perl, Lua, R, Julia, OCaml, Crystal, Nim, Zig, and D.
import_registry_test.go	Adds tests validating Imports behavior for the newly supported languages.
README.md	Updates documented language coverage for import + reference extraction.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.