fix(ruby): emit inherits edge for class superclass

[Synvoya]

Summary

The Ruby extractor silently drops every class inheritance edge. class Dog < Animal produces contains/method/call edges but no inherits edge.

Root cause

Ruby exposes the base class in the superclass field:

class <name=constant, superclass=superclass, body=body_statement>
  superclass -> '<' + constant "Animal"

The inheritance handler in _extract_generic has dedicated branches for java, kotlin, c#, scala, cpp, php, swift, and python — but none for Ruby, so the superclass field is never read.

Fix

Add a Ruby branch that reads the superclass field and emits an inherits edge, handling both forms:

• bare constant: class Dog < Animal -> Animal
• qualified: class Cat < M::Base (scope_resolution) -> Base

It reuses the same synthesize-base-node-if-absent + add_edge pattern as the other language branches.

Verification

• Added a subclass to the Ruby fixture and a regression test.
• pytest tests/test_languages.py -> 268 passed, 13 skipped (existing Ruby tests unaffected).
• ruff check --config pyproject.toml -> clean.

Before / after

class Dog < Animal

• before: only contains
• after: inherits Dog->Animal

[safishamsi]

Merged into v8 as a19b9e9 (your authorship). Verified: exactly one ApiClient node (no duplicate) and the inherits edge targets the real class node with its source_file intact — the synth-if-absent path correctly resolves to the existing definition. Handles bare and M::Base qualified forms. Full suite 2767 passed. Ships next release.