feat(iso): orientation-aware walls + floor variety + juice (shadows/vignette)

Fixes the "thin disconnected slabs" on the top-left/bottom-right walls and juices
the iso scene:
- Wall facing: iso walls have an orientation. A run along grid-x uses the _S
  rotation, a run along grid-y uses the perpendicular _W (I viewed the tiles:
  _S faces SW, _W faces SE — the two camera-facing rotations), and true corners
  use the corner tile. The renderer picks per-cell from neighbours. Enclosing
  walls now read as continuous faces on all four edges. Same logic gives
  windows/doors a Y rotation.
- Floor variety: deterministic per-cell hash sprinkles planksBroken into wood
  floors and stoneTile/stoneUneven into stone — no more flat identical sea.
- Juice: soft contact shadows ground every prop + character, and a warm radial
  vignette lights the room instead of it looking pasted onto black.
- Tavern map: barrels/crates line the side walls (clear of windows/spawn, via
  the wall-safe put()) so the lobby reads lived-in in every render mode.

Suite 58/419 green.

src/multiplayer/tavernMap.js

@@ -51,6 +51,16 @@ function buildDefaultTavern(cols = 28, rows = 15) {
     // Corner decor — barrels and crates.
     put(1, 1, 'B'); put(cols - 2, 1, 'C'); put(1, rows - 2, 'C'); put(cols - 2, rows - 2, 'B');
 
+    // Barrels & crates lining the side walls (one in from the wall, clear of the windows/spawn) so
+    // the room reads lived-in instead of a big empty floor. Alternating B/C for material variety.
+    const wallDecor = [
+        [1, 5, 'B'], [1, 9, 'C'], [1, 12, 'B'],
+        [cols - 2, 5, 'C'], [cols - 2, 9, 'B'], [cols - 2, 12, 'C'],
+        [2, rows - 2, 'B'], [cols - 3, rows - 2, 'C'],
+        [barX0 - 1, barY + 1, 'B'], [barX1 + 1, barY + 1, 'C'] // a barrel/crate tucked beside each keg
+    ];
+    for (const [dx, dy, dch] of wallDecor) put(dx, dy, dch);
+
     // Door + spawn pad at the bottom-centre (two spawn tiles for deterministic adjacency tests).
     const mid = Math.floor(cols / 2);
     set(mid, rows - 1, 'D');