Let a function node's own settings be edited

A python node's params reach process() as whatever its author put there,
but there was no way to put anything there: the settings form is built
from a type's declared schema, and a function node declares none.

Node types now say whether they take settings beyond their schema, and
the panel offers a key/value editor for the ones that do — named, typed
as text, number, on/off or JSON, and laid out like the port list beside
it. Rows are keyed by position rather than by name, so renaming a setting
does not remount the row and lose what was being typed into it.

Verified in the running app in both themes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011LF61rxW1FG5YCD2J9YqjY

frontend/src/client/schemas.gen.ts

@@ -831,6 +831,11 @@ export const NodeTypeInfoSchema = {
             title: 'Has Source',
             default: false
         },
+        free_params: {
+            type: 'boolean',
+            title: 'Free Params',
+            default: false
+        },
         plugin: {
             anyOf: [
                 {

frontend/src/client/types.gen.ts

@@ -264,6 +264,7 @@ export type NodeTypeInfo = {
         [key: string]: unknown;
     };
     has_source?: boolean;
+    free_params?: boolean;
     plugin?: (string | null);
 };