fix(scala): capture trait declarations as class-like nodes

[Synvoya]

Bug

Scala trait declarations produce no node and no heritage edges. A trait that extends/with-mixes other types loses all of that structure.

Root cause

_SCALA_CONFIG.class_types contained only class_definition and object_definition. The tree-sitter-scala grammar parses a trait as a trait_definition node, which was therefore never treated as class-like — so it never became a node and the Scala heritage handler never ran for it.

Minimal repro

trait Greeter extends Base with Logging { def greet(): Unit }

Before: no Greeter node, no inherits/mixes_in edges.

Fix

Add trait_definition to _SCALA_CONFIG.class_types. The existing Scala extends_clause handler already splits the first base (inherits) from subsequent with mixins (mixes_in), so once the trait becomes a class-like node the edges are emitted correctly.

After the fix:

• Greeter --inherits--> Base
• Greeter --mixes_in--> Logging

Testing

• Added test_scala_trait_definition_heritage to tests/test_languages.py, mirroring the existing test_scala_splits_inherits_and_mixes_in. Fails before, passes after.
• tests/test_languages.py: 315 passed, 13 skipped.