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

backend/tests/flow/test_store.py

@@ -43,9 +43,7 @@ def test_every_change_is_committed(store: FlowStore):
     store.write_flow(a_flow())
     assert commit_count(store) == before + 1
 
-    store.write_node_source(
-        "heating", "sensor", "def process(params):\n    return {}\n"
-    )
+    store.write_node_source("heating", "sensor", "def process():\n    return {}\n")
     assert commit_count(store) == before + 2
 
 
@@ -65,9 +63,7 @@ def test_missing_flow_is_reported(store: FlowStore):
 
 def test_deleting_removes_flow_and_its_nodes(store: FlowStore):
     store.write_flow(a_flow())
-    store.write_node_source(
-        "heating", "sensor", "def process(params):\n    return {}\n"
-    )
+    store.write_node_source("heating", "sensor", "def process():\n    return {}\n")
 
     store.delete_flow("heating")
 
@@ -77,9 +73,7 @@ def test_deleting_removes_flow_and_its_nodes(store: FlowStore):
 
 def test_renaming_a_flow_carries_its_nodes(store: FlowStore):
     store.write_flow(a_flow())
-    store.write_node_source(
-        "heating", "sensor", "def process(params):\n    return {}\n"
-    )
+    store.write_node_source("heating", "sensor", "def process():\n    return {}\n")
 
     renamed = store.rename_flow("heating", "warmth")