Refit the canvas on any layout change, not just window resize (topbar-wrap bug)

On a narrow window the topbar's flex-wrap pushes its actions (the Help "?" among
them) onto a second line, growing the topbar and shrinking the view below it —
but that fires no window `resize` event, so resizeCanvas never ran. The backing
store kept its old, taller size: the never-redrawn strip showed as a thick band
at the bottom of the view, and because the render viewport and the click→world
transform then disagreed on the canvas height, every selection landed offset.

A ResizeObserver on the canvas refits the backing store the instant its box
changes — covering the topbar wrap, the Home button appearing, and the portrait
sheet collapse in one place — and re-clamps the camera into the map. Verified in
a real browser: narrowing to 460px wraps the topbar to 83px and the backing
store tracks the new client box exactly (no stale strip, no offset).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AEQUVetLk31Jj7niDQAsXL

main.js

@@ -55,6 +55,23 @@ function resizeCanvas() {
 }
 window.addEventListener("resize", resizeCanvas);
 
+// The canvas fills a flex region, so its box can change from a LAYOUT shift that fires NO window
+// `resize` event — most visibly the topbar wrapping to a second line on a narrow window (its
+// `flex-wrap` grows it, shrinking the view below), but also the Home button appearing or the
+// portrait sheet collapsing. Without a refit, resizeCanvas never ran: the backing store kept its
+// old, taller size, so the never-redrawn strip showed as a thick band at the bottom AND — because
+// the render viewport and the click→world transform then disagreed on the canvas height — every
+// selection landed offset. A ResizeObserver refits the backing store the instant the box changes,
+// in one place (superseding the ad-hoc triggers above), and re-clamps the camera into the map.
+if (window.ResizeObserver) {
+  new ResizeObserver(() => {
+    resizeCanvas();
+    if (game.state && game.input) {
+      clampCamera(game.input.getCamera(), game.state.map, canvas.clientWidth, canvas.clientHeight);
+    }
+  }).observe(canvas);
+}
+
 // A monitor move (or an OS scaling change) can change devicePixelRatio WITHOUT firing a resize
 // event — the CSS layout size is unchanged — leaving the backing store at the old DPR (blurry on
 // the sharper screen, oversampled on the other). matchMedia on the current dppx fires once when