Replace raw node input indices with compile-time parameter symbols (#4387)

* Remove the dead InputAccessor traits and the uncallable test helper built on them

* Replace raw node input indices with macro-generated parameter symbols across the editor

* Audit dynamic input index usage, converting to parameter symbols and named input position constants

* Abstract the remaining input index plumbing behind ParameterRef APIs and accessors

* Build SetInputValue messages as struct literals to keep message enums impl-free

* Delete the typed parameter markers in favor of explicit-output test introspection

* Wire the interpolation control path input per chain node type

* Return no input when a parameter symbol is read against the wrong node's parameter view

node-graph/node-macro/src/lib.rs

@@ -1,7 +1,6 @@
 use crate::crate_ident::CrateIdent;
 use proc_macro::TokenStream;
 use proc_macro_error2::proc_macro_error;
-use syn::GenericParam;
 
 mod buffer_struct;
 mod codegen;