Record flags in history and draw them as steps

A bool was excluded from the history as "not a measurement", so a true/false
port had no curve in the node panel and none on an edge — only the word. It is
recorded as 0/1 now and drawn as steps, since a bezier through two states
slopes through readings that never happened. The axis is pinned to 0..1, so a
flag that was never on sits at the floor rather than mid-box.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

frontend/src/components/Flow/EdgeInspector.tsx

@@ -132,11 +132,11 @@ export function EdgeInspector({
         </div>
 
         {/* The same curve the node panel draws for this message: one value
-            says little, how it has been moving says the rest. Only for a
-            number, because only numbers are recorded — for anything else the
-            sparkline falls through to its own copy of the value, which the
-            popover already shows below. */}
-        {typeof live?.value === "number" ? (
+            says little, how it has been moving says the rest. Only for what is
+            recorded — a number, or a flag as the steps between 0 and 1. For
+            anything else the sparkline falls through to its own copy of the
+            value, which the popover already shows below. */}
+        {typeof live?.value === "number" || typeof live?.value === "boolean" ? (
           <div className="mt-2">
             <MessageSparkline
               flow={flow}

frontend/src/components/Flow/MessageSparkline.tsx

@@ -83,11 +83,13 @@ export function MessageSparkline({
   const ts = live?.ts
   const value = live?.value
   useEffect(() => {
-    if (typeof value !== "number" || !ts) return
+    // A flag is recorded as 0/1, the way the server keeps it.
+    if ((typeof value !== "number" && typeof value !== "boolean") || !ts) return
+    const reading = Number(value)
     setTail((previous) =>
       previous[previous.length - 1]?.ts === ts
         ? previous
-        : [...previous, { ts, value }].slice(-WINDOW),
+        : [...previous, { ts, value: reading }].slice(-WINDOW),
     )
   }, [ts, value])
 
@@ -127,7 +129,10 @@ export function MessageSparkline({
     <Tooltip>
       <TooltipTrigger asChild>
         <div>
-          <Sparkline points={points} />
+          <Sparkline
+            points={points}
+            bool={dtype === "bool" || typeof live?.value === "boolean"}
+          />
         </div>
       </TooltipTrigger>
       <TooltipContent>{caption(points)}</TooltipContent>