feat(monetization): lock the cosmetic ladder (loyalty model) + free Original pack

Nails down the premium unlock system per the design pass:
- FREE `original` topdown pack (NEW): the game's bare tiles — floor/wall/door/
  torch/features only, no furniture, so the free tavern reads plain (the intended
  "reason to unlock"). Registered in assetPacks (RK.THEMES.original) as the free
  default topdown pack; plain ASCII stays free (accessibility).
- Loyalty ladder (lifetime credits PURCHASED, cumulative, NOT deducted → buying to
  play also unlocks cosmetics): Interior 1, skins 5, iso 10, +tilepack 20, +iso 40,
  3D 50. Each row is data (tilepack OR skin) → operator appends more at any rung.
  DEFAULT_CATALOG (entitlements.js) + migration 028 + MONETIZATION.md ladder table.
- Tests updated to the new thresholds (catalogEntitlements_ultra, directEntryCredit_ultra).

Note: this reprices roguelike-interior from free → 1cr, so once deployed the free
tavern becomes bare (by design). Deploy is bundled with the single-player render-kit
migration so the free-tier change lands with its payoff. Suite 61/432 green.

html/js/render/assetPacks.js

@@ -130,6 +130,25 @@
     };
 
     RK.THEMES = {
+        // FREE baseline pack — the game's original bare tiles. Only the essentials are mapped
+        // (floor/wall/door/torch/features); furniture kinds (bar/keg/table/chair/…) are absent, so
+        // they fall back to floor and the free tavern reads plain — the intended "reason to unlock".
+        'original': {
+            id: 'original',
+            label: 'Original Tiles',
+            tileset: { url: 'assets/kenney/roguelikeSheet.png', tile: 16, spacing: 1 },
+            tiles: {
+                floor: [5, 2],      // wood floor
+                floor2: [6, 2],     // stone accent
+                wall: [13, 12],     // masonry
+                door: [37, 9],
+                entrance: [37, 9],
+                exit: [37, 9],
+                treasure: [42, 15],
+                torch: [50, 10]
+                // No furniture kinds → bar/keg/table/chair/shelf/barrel/crate/rug fall back to floor.
+            }
+        },
         'roguelike-interior': {
             id: 'roguelike-interior',
             label: 'Kenney Roguelike Interior',
@@ -387,6 +406,7 @@
     // projection is entitlement-gated + user-selectable. Adding a pack later = registerPack(...) +
     // assets + a catalog row. Backward-compatible: one pack per projection resolves to these.
     if (RK.registerPack) {
+        RK.registerPack({ id: 'original', label: 'Original Tiles', projection: 'topdown', kind: 'tiles', assets: RK.THEMES['original'] });
         RK.registerPack({ id: 'roguelike-interior', label: 'Roguelike Interior', projection: 'topdown', kind: 'tiles', assets: RK.THEMES['roguelike-interior'] });
         RK.registerPack({ id: 'roguelike-dungeon', label: 'Roguelike Dungeon', projection: 'topdown', kind: 'tiles', assets: RK.THEMES['roguelike-dungeon'] });
         RK.registerPack({ id: 'iso-dungeon', label: 'Isometric Dungeon', projection: 'iso', kind: 'tiles', assets: RK.isoAssets });