Give the panel the canvas, and open a flow already fitted

Opening a node or the flow settings now takes the flowbar and the dock
away, leaving the graph and the panel; they come back on close, leaving
by the same slideUp they arrive with. The panel header names the flow
before the node, `/heating/`, which is how messages are qualified
everywhere else.

Opening a flow already fitted, and pressing Fit to screen, disagreed:
one used a 0.25 padding capped at 1x, the other xyflow's defaults, so
the button visibly jumped and a small flow opened at 100% in an empty
canvas. Both read one constant now.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KkmeRiyeYmVZqJVwuyHq9o

frontend/src/components/Flow/FlowDock.tsx

@@ -25,6 +25,14 @@ import {
 } from "@/components/ui/tooltip"
 import { slideUp, transitions } from "@/lib/motion"
 
+/**
+ * What "fit" means on this canvas: the view a flow opens with, and the one the
+ * fit button returns to. The generous padding keeps the graph clear of the
+ * chrome floating over it, and the cap stops a two-node flow from being blown
+ * up past legibility.
+ */
+export const FIT_VIEW = { padding: 0.25, maxZoom: 1.2 }
+
 /**
  * The action bar, floating bottom-centre. Run is the one brand-secondary
  * affordance on this view; everything else stays quiet.
@@ -49,6 +57,7 @@ export function FlowDock({
       variants={slideUp}
       initial="hidden"
       animate="visible"
+      exit="exit"
       transition={transitions.emphasized}
       className="pointer-events-auto absolute bottom-4 left-1/2 z-10 flex -translate-x-1/2 items-center gap-1 rounded-full border border-border bg-card/80 px-1.5 py-1 shadow-e2 backdrop-blur-md pb-[max(0.25rem,env(safe-area-inset-bottom))]"
     >
@@ -85,7 +94,7 @@ export function FlowDock({
             variant="ghost"
             size="icon"
             className="size-11 text-muted-foreground md:size-8"
-            onClick={() => fitView({ duration: 300 })}
+            onClick={() => fitView({ ...FIT_VIEW, duration: 300 })}
             aria-label="Fit the flow to the screen"
           >
             <Maximize2 />