Function is_known_startup_instructions_filename 

pub fn is_known_startup_instructions_filename(path: &str) -> bool

Whether path matches ANY registered provider’s startup_instructions_filename — used by the “click Launch” RPC write path (editor_handlers.rs’s WriteAgentConfig handler), which receives an already-built file list from the frontend with no accompanying provider ID, so it can’t otherwise tell “this is the startup instructions file” from “this is some other config file” without either re-deriving the mapping itself (drift risk) or checking membership here (single source of truth). See docs/specs/SPEC_PROVIDER_AWARE_STARTUP_INSTRUCTIONS_2026_08_24.md §3.