Document outline drops child variables when a function/filter reuses a variable name declared earlier (scope-blind declaration dedup)

<img width="1386" height="634" alt="Image" src="https://github.com/user-attachments/assets/144414a6-be5f-4f1f-b9fd-104c72b4d3f9" />

Copilot Instructions: Treat filter keyword the same as function in the LSP when an outline for symbols is requested