fix: unlock font-size field for global editing without selection

The font-size input, increment, and decrement buttons were disabled
unless a text node was selected, blocking the global workflow: typing
a value with nothing selected should apply to every text box on the
page, and clearing it should reset all boxes to auto.

What changed:
- Switch the disabled guard from !selectedNode to !hasNodes so the
  controls stay enabled whenever the page has text boxes.
- Route commits through applyStyleToSelected when a node is selected
  and applyStyleToAll otherwise, so the existing per-node behavior is
  preserved.
- Buffer the input in local state (globalFontSizeInput) while in
  global scope, otherwise the controlled value resets to '' on each
  keystroke because currentFontSize stays undefined with no selection.

User-visible behavior differences:
- With no text node selected, the font-size field is now editable
  (previously greyed out). Typing a number applies it to every text
  box on the page; clearing the field resets all boxes to auto.
- Selecting a single text box still applies changes only to that
  node, unchanged.

How I verified:
- bun run format and bun run test:ui (158/158 passed, including new
  tests covering the global behavior).
- Manually confirmed against a running app: with no text node
  selected, typing 24 sets fontSize=24 on all 8 text boxes; clearing
  the field reverts all to auto (null) in the backend scene.

Closes #649.

This patch was made with AI assistance (Devin/Claude). The code was
reviewed and tested before submission.

Author: JoeJoeflyn

ui/components/panels/RenderControlsPanel.tsx

@@ -148,6 +148,14 @@ export function RenderControlsPanel() {
 
   const sectionRef = useRef<HTMLDivElement>(null)
   const [sectionWidth, setSectionWidth] = useState<number>(0)
+  // Buffers font-size input in global scope (no selection) so multi-digit
+  // values can be typed before committing — the controlled `value` would
+  // otherwise reset to '' on each keystroke because `currentFontSize` stays
+  // undefined when nothing is selected.
+  const [globalFontSizeInput, setGlobalFontSizeInput] = useState('')
+  useEffect(() => {
+    setGlobalFontSizeInput('')
+  }, [selectedNode?.id, page?.id])
 
   useEffect(() => {
     if (!sectionRef.current) return
@@ -565,10 +573,20 @@ export function RenderControlsPanel() {
             variant='ghost'
             size='icon-sm'
             className='size-6 shrink-0 rounded-r-none border-r'
-            disabled={!selectedNode}
+            disabled={!hasNodes}
             onClick={() => {
-              const next = Math.max(6, Math.round((currentFontSize ?? 16) - 1))
-              applyStyleToSelected({ fontSize: next })
+              const base = selectedNode
+                ? (currentFontSize ?? 16)
+                : globalFontSizeInput !== ''
+                  ? Number.parseInt(globalFontSizeInput, 10)
+                  : 16
+              const next = Math.max(6, Math.round((Number.isFinite(base) ? base : 16) - 1))
+              if (selectedNode) {
+                applyStyleToSelected({ fontSize: next })
+              } else {
+                setGlobalFontSizeInput(String(next))
+                applyStyleToAll({ fontSize: next })
+              }
             }}
           >
             <MinusIcon className='size-3' />
@@ -581,27 +599,58 @@ export function RenderControlsPanel() {
             inputMode='numeric'
             className='h-6 min-w-0 flex-1 [appearance:textfield] rounded-none border-0 px-0.5 text-center text-xs shadow-none focus-visible:ring-0 [&::-webkit-inner-spin-button]:appearance-none [&::-webkit-outer-spin-button]:appearance-none'
             data-testid='render-font-size'
-            disabled={!selectedNode}
-            value={currentFontSize !== undefined ? Math.round(currentFontSize) : ''}
+            disabled={!hasNodes}
+            value={
+              selectedNode
+                ? currentFontSize !== undefined
+                  ? Math.round(currentFontSize)
+                  : ''
+                : globalFontSizeInput
+            }
             placeholder='auto'
             onChange={(event) => {
-              if (event.target.value === '') {
-                applyStyleToSelected({ fontSize: null })
+              const raw = event.target.value
+              if (selectedNode) {
+                if (raw === '') {
+                  applyStyleToSelected({ fontSize: null })
+                  return
+                }
+                const parsed = Number.parseInt(raw, 10)
+                if (!Number.isFinite(parsed) || parsed < 1) return
+                applyStyleToSelected({ fontSize: Math.min(300, parsed) })
+                return
+              }
+              // Global scope: buffer locally so multi-digit values survive
+              // re-renders, then commit to every text box.
+              setGlobalFontSizeInput(raw)
+              if (raw === '') {
+                applyStyleToAll({ fontSize: null })
+                return
               }
-              const parsed = Number.parseInt(event.target.value, 10)
+              const parsed = Number.parseInt(raw, 10)
               if (!Number.isFinite(parsed) || parsed < 1) return
-              applyStyleToSelected({ fontSize: Math.min(300, parsed) })
+              applyStyleToAll({ fontSize: Math.min(300, parsed) })
             }}
           />
           <Button
             type='button'
             variant='ghost'
             size='icon-sm'
             className='size-6 shrink-0 rounded-l-none border-l'
-            disabled={!selectedNode}
+            disabled={!hasNodes}
             onClick={() => {
-              const next = Math.min(300, Math.round((currentFontSize ?? 16) + 1))
-              applyStyleToSelected({ fontSize: next })
+              const base = selectedNode
+                ? (currentFontSize ?? 16)
+                : globalFontSizeInput !== ''
+                  ? Number.parseInt(globalFontSizeInput, 10)
+                  : 16
+              const next = Math.min(300, Math.round((Number.isFinite(base) ? base : 16) + 1))
+              if (selectedNode) {
+                applyStyleToSelected({ fontSize: next })
+              } else {
+                setGlobalFontSizeInput(String(next))
+                applyStyleToAll({ fontSize: next })
+              }
             }}
           >
             <PlusIcon className='size-3' />

ui/tests/components/RenderControlsPanel.test.tsx

@@ -170,6 +170,61 @@ describe('RenderControlsPanel Font Assignment', () => {
     expect(input).toHaveAttribute('placeholder', 'auto')
   })
 
+  it('typing a font size with no selection applies the size to all text boxes', async () => {
+    renderWithQuery(<RenderControlsPanel />)
+
+    // No selection — global scope
+    const input = (await screen.findByTestId('render-font-size')) as HTMLInputElement
+    expect(input).not.toBeDisabled()
+
+    await userEvent.clear(input)
+    await userEvent.type(input, '24')
+
+    await waitFor(() => expect(sceneActions.applyOp).toHaveBeenCalled())
+    const op = (sceneActions.applyOp as any).mock.calls.at(-1)[0]
+    expect(op).toHaveProperty('batch')
+    expect(op.batch.ops).toHaveLength(2)
+    for (const sub of op.batch.ops) {
+      expect(sub.updateNode.patch.data.text.style.fontSize).toBe(24)
+    }
+  })
+
+  it('clearing the font size with no selection resets all boxes to auto', async () => {
+    server.use(
+      http.get('/api/v1/scene.json', () =>
+        HttpResponse.json(
+          sceneWithTextNodes([
+            {
+              id: 't1',
+              kind: { text: { style: { fontFamilies: ['Arial'], fontSize: 20 } } },
+            },
+            {
+              id: 't2',
+              kind: { text: { style: { fontFamilies: ['Arial'], fontSize: 20 } } },
+            },
+          ]),
+        ),
+      ),
+    )
+
+    renderWithQuery(<RenderControlsPanel />)
+
+    const input = (await screen.findByTestId('render-font-size')) as HTMLInputElement
+    // Type a value first so the buffer has content to clear.
+    await userEvent.type(input, '30')
+    await userEvent.clear(input)
+
+    await waitFor(() => {
+      const calls = (sceneActions.applyOp as any).mock.calls
+      expect(calls.length).toBeGreaterThan(0)
+      const op = calls.at(-1)[0]
+      expect(op).toHaveProperty('batch')
+      for (const sub of op.batch.ops) {
+        expect(sub.updateNode.patch.data.text.style.fontSize).toBeNull()
+      }
+    })
+  })
+
   it('opening the font color picker commits effective black as an explicit color', async () => {
     server.use(
       http.get('/api/v1/scene.json', () =>