Node settings arrive as keyword arguments, not a params dict

A python node's settings are constants of its own function, so they are passed
the way its ports are: by name. The controller binds them to the compiled
function, the `params` field is gone from the worker and remote protocols, and
a setting sharing a port's name is reported as a node error rather than
shadowing it. The panel's scaffold follows suit and keeps the header in step
with both ports and settings.

The demo's `pace` moves from a flow input to a setting of the training node,
which is what it always was.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NUb8YpL2s3gmN9WTACTt4q

frontend/tests/flows.spec.ts

@@ -101,12 +101,12 @@ test("running a flow puts values on its edges", async ({ page }) => {
   await setNodeSource(
     page,
     "python",
-    'def process(params):\n    return {"reading": 42.0}\n',
+    'def process():\n    return {"reading": 42.0}\n',
   )
   await setNodeSource(
     page,
     "python_2",
-    "def process(reading, params):\n    return {}\n",
+    "def process(reading):\n    return {}\n",
   )
 
   await page.reload()