fix(abc/kotlin): primary-constructor superclass call is not a branch

[dekobon]

Summary

Kotlin ABC counts a secondary-constructor superclass delegation
(constructor_delegation_call, : super(x)) as a branch but not the
primary-constructor form (constructor_invocation, class Sub : Base(1, 2)). Both invoke the superclass constructor at run time.
#1279 added the first and did not name the second.

Measured

bca metrics --no-config -O json, abc.branches:

class Sub1 : Base(1, 2) { }
class Sub2 : Base { constructor(x: Int) : super(x) { } }

space	abc.branches
Sub1	0
Sub2	1

bca dump shows the two productions:

{delegation_specifier:167} : Base(1, 2)
  {constructor_invocation:162} : Base(1, 2)      <- not counted
...
{constructor_delegation_call:154} : super(x)     <- counted

Where

kotlin_count_token_branch / the branch arm in
src/metrics/abc/kotlin.rs lists CallExpression,
ConstructorDelegationCall and the object-construction kinds, but not
ConstructorInvocation.

Sibling comparison

• C#: constructor_initializer (: base(…) / : this(…)) counts —
  added by fix(abc): constructor delegation calls score zero branches in Java and C# #1279 and pinned by
  csharp_constructor_initializer_is_a_branch.
• Java and Groovy: class Sub extends Base carries no argument list, so
  there is no analogous production to miss; their super(1) inside a
  constructor body is a CallExpression and already counts.

Kotlin's primary-constructor form is the only spelling of "call the
superclass constructor" that scores zero.

Notes

Found while fixing #1297 (kotlin_super_type_argument_is_not_a_condition
uses class B : A() as scaffolding and its branches_sum() anchor
measured 1, not 2). Not fixed there — it is a branches question, not a
conditions one, and unrelated to the < / > token class that issue
covers.

ConstructorInvocation also appears in an enum-entry initialiser
(enum class E { A(1) }) and a delegation specifier with no arguments
is a plain user_type, not a constructor_invocation, so the arm can
be added without a parent gate — but confirm that with a bca dump
sweep before landing it, and check the nom / wmc / cyclomatic
siblings for the same omission.