Address touch review: one coarse-pointer signal + stable nudge callbacks

Gadfly on #104:
- The handles keyed off `pointer: coarse` but the NudgePad off `md:hidden`
  (viewport), so a large touchscreen or a narrow mouse window got them
  disagreeing. Extracted one `isCoarsePointer` in shared.ts that both use —
  the pad now shows on a coarse pointer, same as the bigger handles.
- Wrapped commitLater/nudgeSelected in useCallback([]) — stable identity, so
  NudgePad doesn't re-render each parent render, and the mount-once keydown
  effect capturing nudgeSelected is now explicitly safe (a comment spells out
  the refs-only invariant that makes the empty-deps capture correct).
- isCoarsePointer's optional-chained matchMedia keeps it false (mouse
  defaults) under test/SSR, addressing the constants-file testability note.

tsc + build green.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01H3zbym8Doka2d7D48maSgZ

web/src/editor/shared.ts

@@ -3,12 +3,17 @@
 // one place instead of drifting between files.
 
 export const SELECT_COLOR = '#2f7a3e' // selection stroke/handles
-// On-screen size of a drag/resize handle. Bigger on a coarse pointer (touch) so
-// a fingertip can actually grab a resize corner or the rotate knob — 12px is fine
-// for a mouse but frustrating for a thumb (#104). Read once at load; a device
-// doesn't switch its primary pointer mid-session.
-export const HANDLE_PX =
-  typeof window !== 'undefined' && window.matchMedia?.('(pointer: coarse)').matches ? 22 : 12
+// Whether the primary pointer is a fingertip rather than a mouse — the one signal
+// the touch affordances key off (bigger handles here, the on-screen nudge pad in
+// the editor), so they can't disagree about what "touch" means. Read once at
+// load; a device doesn't switch its primary pointer mid-session, and the optional
+// chain keeps it false (mouse defaults) under test / SSR where matchMedia is absent.
+export const isCoarsePointer =
+  typeof window !== 'undefined' && !!window.matchMedia?.('(pointer: coarse)').matches
+// On-screen size of a drag/resize handle. Bigger on touch so a fingertip can
+// actually grab a resize corner or the rotate knob — 12px is fine for a mouse but
+// frustrating for a thumb (#104).
+export const HANDLE_PX = isCoarsePointer ? 22 : 12
 export const MIN_RADIUS_CM = 1 // smallest plop radius
 export const DIMMED_OPACITY = 0.4 // non-focused objects/plops in focus mode
 

web/src/pages/GardenEditorPage.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useMemo, useRef, useState } from 'react'
+import { useCallback, useEffect, useMemo, useRef, useState } from 'react'
 import { getRouteApi } from '@tanstack/react-router'
 import { Alert } from '@/components/ui/Alert'
 import { Button } from '@/components/ui/Button'
@@ -18,6 +18,7 @@ import { EditorHint } from '@/editor/EditorHint'
 import { SeasonBanner, SeasonPicker } from '@/editor/SeasonPicker'
 import { objectDisplayName } from '@/editor/kinds'
 import { useEditorStore, type EditorMode } from '@/editor/store'
+import { isCoarsePointer } from '@/editor/shared'
 import { cn } from '@/lib/cn'
 import type { EditorGarden } from '@/editor/types'
 import { ShareGardenModal } from '@/components/gardens/ShareGardenModal'
@@ -289,7 +290,11 @@ export function GardenEditorPage() {
   // object's local bounds. Reads live values from getState/nudgeCtx so it's
   // correct whichever surface calls it; a commit only fires if its live value is
   // still present (a drag that cleared it already committed its own PATCH).
-  const commitLater = (fire: () => void) => {
+  // Stable across renders (empty deps): both read live values through refs
+  // (nudgeCtx) / getState, never through closed-over props, so a mount-once
+  // consumer (the keydown effect) and a memo-friendly one (NudgePad) both get a
+  // function that stays current without a new identity each render.
+  const commitLater = useCallback((fire: () => void) => {
     nudgeFire.current = fire
     if (nudgeTimer.current != null) window.clearTimeout(nudgeTimer.current)
     nudgeTimer.current = window.setTimeout(() => {
@@ -298,9 +303,9 @@ export function GardenEditorPage() {
       nudgeFire.current = null
       fn?.()
     }, 400)
-  }
+  }, [])
 
-  const nudgeSelected = (dx: number, dy: number) => {
+  const nudgeSelected = useCallback((dx: number, dy: number) => {
     const { canEdit: canNudge, objects: objs, plantings: plops, updateObject: uo, updatePlanting: up } =
       nudgeCtx.current
     if (!canNudge) return
@@ -335,7 +340,7 @@ export function GardenEditorPage() {
         useEditorStore.getState().setLivePlanting(null)
       })
     }
-  }
+  }, [commitLater])
 
   // Keyboard nudging (desktop): arrows move the selection 1cm, Shift = 10cm — the
   // same nudgeSelected the touch pad uses. Mounted once; a pending commit is
@@ -636,9 +641,10 @@ export function GardenEditorPage() {
         <div className="relative min-h-0 flex-1">
           <GardenCanvas garden={garden} objects={objects} plantings={plantings} plantsById={plantsById} canEdit={canEdit} />
           {/* Touch fine-positioning: the keyboard's arrow-nudge has no equivalent
-              on a phone, and dragging can't hit single-cm precision. Shown while
-              something's selected on a touch layout (#104). */}
-          {canEdit && (selectedId != null || selectedPlantingId != null) && (
+              on a touch device, and dragging can't hit single-cm precision. Shown
+              on a coarse pointer (same signal as the bigger handles) while
+              something's selected (#104). */}
+          {canEdit && isCoarsePointer && (selectedId != null || selectedPlantingId != null) && (
             <NudgePad onNudge={nudgeSelected} />
           )}
         </div>
@@ -836,10 +842,10 @@ function FillControl({ onFill, busy }: { onFill: (layout: FillLayout) => void; b
   )
 }
 
-// On-screen nudge pad (#104): 1cm arrows for the selected object/plop on touch,
-// where the keyboard's arrow-nudge isn't reachable and a drag can't hit single-cm
-// precision. md:hidden — desktop uses the keyboard. Wired to the same
-// nudgeSelected, so it shares the live-then-debounced-PATCH behaviour.
+// On-screen nudge pad (#104): 1cm arrows for the selected object/plop on a touch
+// device, where the keyboard's arrow-nudge isn't reachable and a drag can't hit
+// single-cm precision. Rendered only on a coarse pointer (the caller gates it).
+// Wired to the same nudgeSelected, so it shares the live-then-debounced-PATCH.
 function NudgePad({ onNudge }: { onNudge: (dx: number, dy: number) => void }) {
   const btn =
     'flex size-10 items-center justify-center rounded-md border border-border bg-surface/90 text-fg ' +
@@ -848,7 +854,7 @@ function NudgePad({ onNudge }: { onNudge: (dx: number, dy: number) => void }) {
     <div
       role="group"
       aria-label="Nudge selection by 1cm"
-      className="absolute bottom-2 left-2 z-20 grid grid-cols-3 grid-rows-3 gap-0.5 md:hidden"
+      className="absolute bottom-2 left-2 z-20 grid grid-cols-3 grid-rows-3 gap-0.5"
     >
       <span />
       <button type="button" className={btn} aria-label="Nudge up" onClick={() => onNudge(0, -1)}>