Add flow settings, pulse emitting nodes, and simplify node state

- One dot per node now carries the whole story: primary while running, sage
  after a good run, red when anything is wrong, with the explanation on hover.
  The corner badge is gone, along with the second way of saying the same thing.
- A node that publishes something flashes a ring, so a running flow is legible
  without reading the edge values. Nodes that consume but publish nothing stay
  quiet, which is why the event carries an output count.
- Flow settings open in the same panel its nodes use, from a pencil in the
  dock: the title, the name, and deleting the flow. NodePanel and FlowPanel
  share the panel chrome rather than each drawing their own.
- Renaming is a server operation, because a flow's name is the namespace of its
  messages: the directory moves and every other flow reading `old.message` is
  repointed, instead of being left pointing at a flow that no longer exists.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016WzrvW7rjQbynnhF6pxh6i

frontend/src/components/Flow/FlowDock.tsx

@@ -3,6 +3,7 @@ import {
   AlertCircle,
   Loader2,
   Maximize2,
+  Pencil,
   Play,
   Plus,
   ZoomIn,
@@ -33,12 +34,14 @@ export function FlowDock({
   issues,
   running,
   onAddNode,
+  onEditFlow,
   onRun,
   onFocusNode,
 }: {
   issues: ValidationIssue[]
   running: boolean
   onAddNode: () => void
+  onEditFlow: () => void
   onRun: () => void
   onFocusNode: (nodeId: string) => void
 }) {
@@ -68,6 +71,22 @@ export function FlowDock({
         <TooltipContent>Add a node (⌘K)</TooltipContent>
       </Tooltip>
 
+      <Tooltip>
+        <TooltipTrigger asChild>
+          <Button
+            variant="ghost"
+            size="icon"
+            className="size-11 text-muted-foreground md:size-8"
+            onClick={onEditFlow}
+            aria-label="Flow settings"
+            data-testid="edit-flow"
+          >
+            <Pencil />
+          </Button>
+        </TooltipTrigger>
+        <TooltipContent>Flow settings</TooltipContent>
+      </Tooltip>
+
       <Separator orientation="vertical" className="mx-0.5 !h-5" />
 
       <Button