fix(powershell): emit inherits/implements edges for class base types

The `class_statement` handler read only the first `simple_name` child —
the class name — and never inspected the base type(s) after the `:`
token. As a result `class Dog : Animal` dropped the Dog->Animal
inheritance edge entirely; derived classes appeared as isolated nodes.

Walk the class_statement children, and once the `:` token is seen treat
each following `simple_name` as a base type. Matching the C# convention
(PowerShell has no syntactic base-vs-interface split), the first base is
emitted as `inherits` and the rest as `implements`, resolved via
ensure_named_node.

Adds a Shape/Circle inheritance pair to tests/fixtures/sample.ps1 and a
regression test asserting ("Circle","Shape") in the inherits edges.

tests/fixtures/sample.ps1

@@ -30,3 +30,19 @@ class DataProcessor {
         Set-Content -Path $path -Value $this.Source
     }
 }
+
+class Shape {
+    [string]$Kind
+
+    [double] Area() {
+        return 0.0
+    }
+}
+
+class Circle : Shape {
+    [double]$Radius
+
+    [double] Area() {
+        return 3.14159 * $this.Radius * $this.Radius
+    }
+}

tests/test_languages.py

@@ -1631,6 +1631,13 @@ def test_powershell_finds_class_and_method():
     assert any("Transform" in l for l in labels)
 
 
+def test_powershell_class_base_type_emits_inherits_edge():
+    # `class Circle : Shape` — the base type after ':' was previously dropped
+    # because the handler only read the first simple_name (the class name).
+    r = extract_powershell(FIXTURES / "sample.ps1")
+    assert ("Circle", "Shape") in _edge_labels(r, "inherits")
+
+
 def test_powershell_property_field_type_context():
     r = extract_powershell(FIXTURES / "sample.ps1")
     assert ("DataProcessor", "string") in _edge_labels(r, "references", "field")