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

[Synvoya]

Bug

A Scala class that extends a qualified type emits no heritage edges. class Foo extends pkg.Base with other.Trait1 produces neither an inherits nor a mixes_in edge.

Root cause

The Scala extends_clause handler iterated the clause children matching only type_identifier and generic_type. A qualified base parses as a stable_type_identifier:

extends_clause
  stable_type_identifier "pkg.Base"    -> identifier "pkg" . type_identifier "Base"
  with
  stable_type_identifier "other.Trait1"

Neither branch matched, so both bases were skipped.

Minimal repro

class Foo extends pkg.Base with other.Trait1

Before: no inherits/mixes_in edges.

Fix

Add a stable_type_identifier branch that reads the tail (type_)identifier segment (the real type name, not the package path), consistent with the qualified-base handling for C++ (qualified_identifier) and Kotlin. First base after extends stays inherits; each with mixin stays mixes_in.

After the fix:

• Foo --inherits--> Base
• Foo --mixes_in--> Trait1

Testing

• Added test_scala_qualified_extends_uses_tail_name to tests/test_languages.py. Fails before, passes after.
• tests/test_languages.py: 315 passed, 13 skipped — the existing unqualified Scala heritage test still passes.