follow-up: add juxt_function_call support to Groovy extractor (both engines)

[carlos-alm]

Deferred from PR #1101 review.

Original reviewer comment: #1101 (comment)

Context:
The tree-sitter-groovy grammar produces juxt_function_call nodes for Groovy command-style calls like foo bar(x). Neither the JS source-of-truth extractor (src/extractors/groovy.ts) nor the new Rust port (crates/codegraph-core/src/extractors/groovy.rs) dispatches this node kind, so these calls are silently dropped from the call graph.

This is a parity-equal bug in both engines, not a regression introduced by #1101. Fix should:

1. Add juxt_function_call" arm to extractGroovySymbolsinsrc/extractors/groovy.ts` so the JS extractor handles command-style calls.
2. Add juxt_function_call" arm to match_groovy_nodeincrates/codegraph-core/src/extractors/groovy.rs` to mirror.
3. Add a fixture test exercising command-style calls (e.g. task someTask { ... } Gradle DSL pattern).