fix(scala): emit heritage edges for qualified extends/with clauses

[Synvoya]

Bug

Scala qualified parents were either dropped or retained as package-qualified labels. For example, class Foo extends pkg.Base with other.Trait should emit Foo -> Base and Foo -> Trait.

Root cause

The heritage walker handled type_identifier and a narrow generic_type shape. Qualified parents parse as stable_type_identifier; qualified generic parents wrap that node inside generic_type.

Fix

Normalize heritage nodes through one bounded helper:

• plain type_identifier returns its name;
• stable_type_identifier returns its final type segment;
• generic_type recursively normalizes its base type.

Only direct heritage children are considered, so package segments, generic arguments and constructor arguments cannot become parent edges. The first parent remains inherits; subsequent with parents remain mixes_in.

Validation

• Covers simple qualified parents.
• Covers qualified generic parents.
• Covers multi-segment packages and constructor arguments.
• Verifies package qualifiers and generic arguments are not emitted as parents.
• tests/test_languages.py: 319 passed, 13 optional-DM skips.
• Ruff and git diff --check: passed.

[Synvoya]

Follow-up audit against current v8 found that qualified generic parents such as pkg.Base[Int] still retained the package prefix through the generic_type path. The branch now normalizes both plain and generic qualified parents to the tail type name and extends the regression test. Current validation: tests/test_languages.py 319 passed, 13 skipped; Ruff and git diff --check passed.