fix(scripts): enclosingDeclaration recognises a CLASS METHOD header, so a method code helper is no longer dropped in silence (#13428)

* fix(devx): teach enclosingDeclaration the class-method header form

WIP: recognizer + call-site receiver. Ledger and pins follow.

* fix(devx): rewrite the blindness ledger and pins for the closed declaration form

* fix(devx): make isMethod exclusive with isConstructor; correct the keyword-list claim

* test(devx): repair a vacuous signature pin found by ablation

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Co-authored-by: Claude <noreply@anthropic.com>

Author: os-project-manager