Touch interaction model for coarse pointers, desktop unchanged

Gated on matchMedia("(hover: none)") so mouse/trackpad behavior is
untouched:
- Nav zones + edge markers only on the current tile; tapping any other
  tile selects it first. No more accidental traverses on touch.
- Edges always visible on touch (the hover glow becomes the tap
  affordance), glow while pressed via :active. Bands modestly shrunk so
  tile centers stay grab-to-pan.
- No hover ghost preview and no dropzones on touch (they were invisible
  tap traps without hover).
- Two-finger pinch to zoom (pointer-count based, works everywhere).
- Double-tap on empty space resets zoom, mirroring desktop dblclick.
- Kill iOS tap-highlight and long-press callout.

Adds /tmp/touchtest.mjs (15 checks) covering select/traverse/pinch/
double-tap/pan; domtest 52/52, exhaust 9/9, splash 6/6, fuzz clean.

1 files changed, 63 insertions, 13 deletions

diff --git a/public/app.js b/public/app.js
index 95f64d4..1c920ae 100644
--- a/public/app.js
+++ b/public/app.js
@@ -26,6 +26,8 @@ let scale = 1
 let userZoomed = false
 let drag = null
 
+const TOUCH = typeof window.matchMedia === "function" && window.matchMedia("(hover: none)").matches
+
 function aspect(info) {
   return info.h > 0 ? info.w / info.h : 1
 }
@@ -197,19 +199,22 @@ function renderNav(id) {
   const exits = exitsCache.get(id)
   if (!exits) return
   const isCurrent = cur && cur.id === id
+  if (TOUCH && !isCurrent) return
   const nav = document.createElement("div")
   nav.className = "nav"
   for (const ex of exits) {
     const zone = document.createElement("div")
     zone.className = `nav-zone nav-zone-${ex.dir}`
-    zone.addEventListener("pointermove", () => {
-      if (adjacentTile(id, ex.dir)) return
-      cancelHideGhost()
-      showGhost(choosePlacement(id, ex.dir))
-    })
-    zone.addEventListener("pointerleave", () => {
-      scheduleHideGhost()
-    })
+    if (!TOUCH) {
+      zone.addEventListener("pointermove", () => {
+        if (adjacentTile(id, ex.dir)) return
+        cancelHideGhost()
+        showGhost(choosePlacement(id, ex.dir))
+      })
+      zone.addEventListener("pointerleave", () => {
+        scheduleHideGhost()
+      })
+    }
     zone.addEventListener("pointerdown", (e) => e.stopPropagation())
     zone.addEventListener("click", (e) => { e.stopPropagation(); traverseFrom(id, ex.dir) })
     if (!adjacentTile(id, ex.dir) && isCurrent) {
@@ -389,6 +394,7 @@ function clearAllZones() {
 
 function renderTileZones(id) {
   clearTileZones(id)
+  if (TOUCH) return
   if (!tiles.has(id) || !exitsCache.has(id)) return
   const els = []
   for (const dir of ["N", "E", "S", "W"]) {
@@ -425,15 +431,37 @@ stage.addEventListener("pointerover", (e) => {
   if (tileEl) getExits(Number(tileEl.dataset.id))
 })
 
+const pointers = new Map()
+let pinchDist = 0
+
 stage.addEventListener("pointerdown", (e) => {
   if (e.target.closest(".nav-zone")) return
+  pointers.set(e.pointerId, { x: e.clientX, y: e.clientY })
+  stage.setPointerCapture(e.pointerId)
   hideGhost()
-  drag = { x: e.clientX, y: e.clientY, px: panX, py: panY, moved: false, tile: e.target.closest(".tile") }
   world.style.transition = "none"
-  stage.setPointerCapture(e.pointerId)
+  if (pointers.size === 2) {
+    drag = null
+    const [a, b] = [...pointers.values()]
+    pinchDist = Math.hypot(b.x - a.x, b.y - a.y)
+    return
+  }
+  drag = { x: e.clientX, y: e.clientY, px: panX, py: panY, moved: false, tile: e.target.closest(".tile") }
 })
 
 stage.addEventListener("pointermove", (e) => {
+  if (pointers.has(e.pointerId)) {
+    pointers.set(e.pointerId, { x: e.clientX, y: e.clientY })
+    if (pointers.size === 2 && pinchDist > 0) {
+      const [a, b] = [...pointers.values()]
+      const d = Math.hypot(b.x - a.x, b.y - a.y)
+      if (d > 0) {
+        zoomAt((a.x + b.x) / 2, (a.y + b.y) / 2, d / pinchDist)
+        pinchDist = d
+      }
+      return
+    }
+  }
   if (!drag) return
   const dx = e.clientX - drag.x
   const dy = e.clientY - drag.y
@@ -446,23 +474,45 @@ stage.addEventListener("pointermove", (e) => {
 })
 
 stage.addEventListener("pointerup", (e) => {
+  const wasPinch = pointers.size >= 2
+  pointers.delete(e.pointerId)
+  if (wasPinch && pointers.size === 1) {
+    const p = [...pointers.values()][0]
+    drag = { x: p.x, y: p.y, px: panX, py: panY, moved: true, tile: null }
+  }
+  pinchDist = 0
   if (!drag) return
   const wasDrag = drag.moved
   const tile = drag.tile
   drag = null
   world.style.transition = ""
-  if (wasDrag || !tile) return
+  if (wasDrag || !tile) {
+    if (!wasDrag && !tile && e.pointerType === "touch") bgTap()
+    return
+  }
   const id = Number(tile.dataset.id)
   if (cur && cur.id === id) return
   setCurrent(id, tiles.get(id).rect)
 })
 
-stage.addEventListener("pointercancel", () => {
-  if (!drag) return
+stage.addEventListener("pointercancel", (e) => {
+  pointers.delete(e.pointerId)
+  pinchDist = 0
   drag = null
   world.style.transition = ""
 })
 
+let lastBgTap = -Infinity
+function bgTap() {
+  const now = performance.now()
+  if (now - lastBgTap < 350) {
+    lastBgTap = 0
+    resetZoom()
+    return
+  }
+  lastBgTap = now
+}
+
 let zoomTimer = 0
 stage.addEventListener("wheel", (e) => {
   e.preventDefault()