fix(parsers): expand static dependency indirection coverage

[mstykow]

Summary

• extend Gradle static dependency recovery beyond buildSrc and version catalogs by resolving same-file literal assignments, ext { ... } properties, and nearby gradle.properties values used through $name, ${name}, and Kotlin val ... by project interpolation
• teach CocoaPods Podfile parsing to follow bounded local require_relative helpers and recover version arguments from simple Ruby hash lookups such as versions['Flipper']
• expand NuGet property resolution from whole-string $(Property) replacements to embedded and chained MSBuild property expansion, then apply that to PackageReference versions and project metadata
• resolve richer Ruby gemspec constant expressions from required local files, including interpolated string constants and simple [...].join('.') version builders
• add one new golden fixture per ecosystem, plus the upgraded existing Gradle props golden, using real-world-style patterns inspired by public repositories

Scope and exclusions

• Included:
  • Gradle: src/parsers/gradle.rs plus new/updated goldens under testdata/gradle-golden/
  • CocoaPods: src/parsers/podfile.rs plus a new Podfile golden under testdata/cocoapods-golden/podfile/with-required-version-hash/
  • NuGet: src/parsers/nuget/utils.rs, src/parsers/nuget/project_file.rs, and a new PackageReference golden under testdata/nuget-golden/package-reference-interpolation/
  • Ruby: src/parsers/ruby.rs plus a new gemspec golden under testdata/ruby-golden/interpolated-constants/
  • focused unit and golden coverage for every new behavior
• Explicit exclusions:
  • no Gradle, Ruby, CocoaPods, or MSBuild execution
  • no broad evaluator/AST rewrite project
  • no attempt to resolve dynamic helper methods, arbitrary control flow, network lookups, or generic import graphs outside the existing bounded parser model

Intentional differences from Python

• These changes continue Provenant's pattern of preferring bounded static resolution over placeholder output or dynamic execution.
• Gradle now resolves more static indirection directly from committed local files (build.gradle[.kts] plus nearby gradle.properties) without evaluating Gradle.
• CocoaPods now recovers version arguments from parseable local Ruby hash helpers instead of requiring fully literal inline strings.
• NuGet now resolves embedded property compositions like $(VersionPrefix)-$(VersionSuffix) when those values are statically available in the project file.
• Ruby gemspec parsing now handles more constant-expression shapes from local required files, but still refuses to execute Ruby or chase arbitrary load paths.

Follow-up work

• Created or intentionally deferred:
  • deferred: broader dynamic Gradle DSL evaluation, arbitrary Ruby/CocoaPods execution semantics, and full MSBuild import/condition evaluation remain intentionally out of scope
  • deferred: Podspec-specific Ruby DSL enhancement work beyond the new Podfile hash-resolution slice
  • validation run during implementation:
    • cargo test test_gradle_properties_and_local_assignments_resolve_interpolation
    • cargo test test_extract_pod_version_from_required_hash
    • cargo test test_csproj_package_reference_resolves_embedded_property_versions
    • cargo test test_extract_gemspec_required_file_interpolated_constants
    • cargo test --features golden-tests test_golden_kotlin_project_properties
    • cargo test --features golden-tests test_golden_groovy6_with_props
    • cargo test --features golden-tests test_golden_podfile_required_version_hash
    • cargo test --features golden-tests test_golden_package_reference_project_with_property_interpolation
    • cargo test --features golden-tests test_golden_interpolated_constants_gemspec
    • cargo test parsers::gradle::tests::
    • cargo test parsers::podfile::tests::
    • cargo test parsers::nuget::nuget_test::tests::
    • cargo test parsers::ruby_test::tests::

Expected-output fixture changes

• Files changed:
  • testdata/gradle-golden/groovy/groovy6-with-props/build.gradle-expected.json
  • testdata/gradle-golden/kotlin/project-properties/build.gradle.kts-expected.json
  • testdata/cocoapods-golden/podfile/with-required-version-hash/Podfile-expected.json
  • testdata/nuget-golden/package-reference-interpolation/IceRpc.Examples.csproj.expected
  • testdata/ruby-golden/interpolated-constants/interpolated_constants.gemspec.expected
• Why the new expected output is correct:
  • each updated expected file now reflects a static value that is already present in committed local companion files or literal constant expressions
  • no fixture depends on executing a build tool or interpreter; every new value comes from bounded parsing of adjacent manifests/helpers
  • the Gradle, CocoaPods, NuGet, and Ruby fixtures each prove a user-visible extraction improvement that was not previously represented in the parser-owned golden corpus