Position the ? popover against the viewport, not inside the dock

Direction was a prop, which only moved the clipping around: the panel is
an overflow-auto box, so a popover below a setting near the bottom is
cut by the dock's edge and one above a control near the top is cut by
its top. The box is `fixed` now, placed from the icon's own rect, so it
leaves the dock altogether -- it prefers up everywhere and flips down
only when the window itself has no room above. Scrolling closes it,
since a fixed box cannot follow its anchor.

Drops the dir prop and the `Change` icon's downward special case.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ui/src/components/OperationPanel.jsx

@@ -98,39 +98,72 @@ const LABEL_W = 'w-24'
 // toggle is skipped, while still costing the dock a row. Hovering gives it
 // (native title, which nothing can clip), clicking pins it.
 //
-// It opens upward, because the settings it explains sit low in a dock that
+// Positioned `fixed` against the icon's own rect rather than absolutely inside
-// scrolls -- a popover hanging below them is cut off by the dock's own edge.
+// it. Absolute meant the dock clipped it: the panel is an overflow-auto box, so
-// `dir="down"` is for the few that sit at the top of the panel, where up is the
+// a popover under a setting at the bottom was cut off by the dock's edge and
-// clipped direction instead.
+// one above a control at the top was cut off by its top. Direction was a prop
-function Help({ text, dir = 'up' }) {
+// for a while, which only moved the clipping around -- fixed leaves the box
-  const [open, setOpen] = useState(false)
+// altogether, so it can prefer up everywhere and flip down only when the window
+// itself has no room.
+const HELP_W = 256   // px; matches the rendered width
+function Help({ text }) {
+  const [at, setAt] = useState(null)
+  const btnRef = useRef(null)
+
+  const place = () => {
+    const r = btnRef.current?.getBoundingClientRect()
+    if (!r) return
+    const left = Math.max(8, Math.min(r.left, window.innerWidth - HELP_W - 8))
+    // Up unless the top of the window is nearer than the box is tall.
+    const up = r.top > 160
+    setAt(up
+      ? { left, bottom: window.innerHeight - r.top + 6 }
+      : { left, top: r.bottom + 6 })
+  }
+
+  useEffect(() => {
+    if (!at) return
+    const close = () => setAt(null)
+    // Any scroll moves the anchor out from under a fixed box, so it closes
+    // rather than floating somewhere it no longer points at.
+    window.addEventListener('scroll', close, true)
+    window.addEventListener('resize', close)
+    return () => {
+      window.removeEventListener('scroll', close, true)
+      window.removeEventListener('resize', close)
+    }
+  }, [at])
+
   if (!text) return null
   return (
-    <span className="relative inline-flex shrink-0">
+    <>
-      <button type="button" title={text} onClick={() => setOpen(o => !o)} onBlur={() => setOpen(false)}
+      <button ref={btnRef} type="button" title={text}
+        onClick={() => (at ? setAt(null) : place())}
+        onBlur={() => setAt(null)}
         aria-label={text}
-        className={`w-4 h-4 rounded-full border leading-none flex items-center justify-center transition-colors ${
+        className={`w-4 h-4 rounded-full border leading-none flex items-center justify-center shrink-0 transition-colors ${
-          open ? 'border-blue-400 text-blue-600 bg-blue-50' : 'border-gray-300 text-gray-500 hover:text-blue-600 hover:border-blue-400'}`}
+          at ? 'border-blue-400 text-blue-600 bg-blue-50' : 'border-gray-300 text-gray-500 hover:text-blue-600 hover:border-blue-400'}`}
         style={{ fontSize: '10px' }}>?</button>
-      {open && (
+      {at && (
-        <span className={`absolute z-20 left-0 w-64 rounded border border-gray-200 bg-white shadow-lg px-2 py-1.5
+        <span
-                          text-gray-600 leading-snug normal-case tracking-normal
+          className="fixed z-50 rounded border border-gray-200 bg-white shadow-lg px-2 py-1.5
-                          ${dir === 'down' ? 'top-5' : 'bottom-5'}`}>
+                     text-gray-600 leading-snug normal-case tracking-normal"
+          style={{ ...at, width: HELP_W }}>
           {text}
         </span>
       )}
-    </span>
+    </>
   )
 }
 
 // `stack` puts the label above its control instead of beside it. The aligned
 // label column costs 6rem, which is most of a narrow zone -- the tag field in
 // the bottom dock had 12rem of box left to type an initiative name into.
-function Field({ label, children, hint, hintDir, stack }) {
+function Field({ label, children, hint, stack }) {
   if (stack) {
     return (
       <div className="flex flex-col gap-1 min-w-0">
-        <span className="text-gray-600 whitespace-nowrap flex items-center gap-1.5">{label}<Help text={hint} dir={hintDir} /></span>
+        <span className="text-gray-600 whitespace-nowrap flex items-center gap-1.5">{label}<Help text={hint} /></span>
         <div className="flex items-center gap-2 min-w-0">{children}</div>
       </div>
     )
@@ -140,7 +173,7 @@ function Field({ label, children, hint, hintDir, stack }) {
       <span className={`text-gray-600 whitespace-nowrap shrink-0 pt-1 ${LABEL_W}`}>{label}</span>
       <div className="flex items-center gap-2 flex-wrap min-w-0">
         {children}
-        <Help text={hint} dir={hintDir} />
+        <Help text={hint} />
       </div>
     </div>
   )
@@ -1540,7 +1573,7 @@ export default function OperationPanel({
           with no heading over it, so the panel never said what it was about
           to do until you read the button. */}
       <div className="flex items-start gap-4 flex-wrap px-3 py-2 border-b border-gray-200 bg-gray-50/60">
-        <Field label="Change" hintDir="down" hint={OP_HELP[activeOp]}>
+        <Field label="Change" hint={OP_HELP[activeOp]}>
           <div className="inline-flex rounded border border-gray-300 divide-x divide-gray-300 shadow-sm overflow-hidden">
             {['scale', 'recode', 'clone'].map(op => (
               <Button key={op} onClick={() => setActiveOp(op)} active={activeOp === op}>