Detect build function by signature, not by name, in referenced-builder contract #319

Sub-task of #301.

Goal

In the contract check for referenced builders (JavaLangAnalyser.hasBuildMethodReturning, called from BuilderScopeResolver.resolveByBuilderContract), detect the build function by signature instead of by name: any public, non-static, parameterless method whose return type is the referenced type T counts — regardless of whether it is named build().

Why

The contract should verify capability, not a naming convention. MapStruct-style and hand-written builders may name the terminal method differently (toTarget(), assemble(), …); a literal build() check rejects builders that would otherwise satisfy the contract. It also aligns the resolver with SimpleBuildersBuilderProvider.findBuildMethods, which already matches build methods by signature (public, non-static, no params, return type == T).

Pitfall

Needs an java.lang.Object-method guard (e.g. toString()): without it, StringBuilder.toString() + StringBuilder(String) satisfy the contract for String — the exact false positive the check is meant to prevent.

Status

Implemented in #320, which closes this issue.