Release v1.3.2: gallery side panel, resizable sidebar, stone textures

- Texture Gallery beside the model with turntable and arrow-key browsing,
  resizable sidebar, uploads saved as "Your textures" (#132)
- New textures: Cobblestone, Flagstone, Square Setts
- Includes the export memory reduction from PR #114
- What's New popup updated; WELCOME_LAST_UPDATED bumped so returning
  visitors see it

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: CNCKitchen

index.html

@@ -791,6 +791,7 @@ <h3 class="welcome-heading">Quick start</h3>
 
       <h3 class="welcome-heading">New in this release <span class="welcome-date">&mdash; September 2026</span></h3>
       <ul class="welcome-changelog">
+        <li><strong>New in v1.3.2</strong> &mdash; the Texture Gallery now opens beside your model, so you can click or arrow-key through textures and see each one live; turn on Turntable to spin the model while you browse. Drag the sidebar&rsquo;s edge to make it wider. Maps you upload are kept under &ldquo;Your textures&rdquo; in this browser. Three new stone textures: Cobblestone, Flagstone and Square Setts. Exporting large models uses about half the memory.</li>
         <li><strong>New textures &amp; Texture Gallery</strong> &mdash; 54 new textures, from knurling and carbon twill to chainmail, bark and dozens of Hero Patterns. Browse them all in the new Texture Gallery with search and categories, and star your favorites to pin them to the panel.</li>
         <li><strong>Smooth masking brush</strong> &mdash; the circle brush now has a Hardness setting: lower it to fade the mask out toward the brush rim for soft, gradual texture borders instead of hard triangle edges. Enable Precision for smooth gradients on coarse meshes.</li>
         <li><strong>ideaMaker textures</strong> &mdash; load .texture files from the <a href="https://www.ideamaker.io/texture" target="_blank" rel="noopener">ideaMaker texture library</a> directly with Upload custom map.</li>

js/main.js

@@ -440,7 +440,7 @@ const imprintClose   = document.getElementById('imprint-close');
 // ── Welcome / What's New popup ───────────────────────────────────────────────
 // Bump this date whenever the "What's New" bullets in index.html change to
 // re-show the popup to all returning visitors who previously dismissed it.
-const WELCOME_LAST_UPDATED = '2026-09-27';
+const WELCOME_LAST_UPDATED = '2026-09-28';
 const WELCOME_STORAGE_KEY  = 'stlt-welcome-seen';
 const welcomeLink     = document.getElementById('welcome-link');
 const welcomeOverlay  = document.getElementById('welcome-overlay');

js/version.js

@@ -7,4 +7,4 @@
 // logged on startup. Keep in sync with package.json when cutting a release.
 // Not to be confused with PROJECT_VERSION in main.js, which versions the
 // .bumpmesh project file format independently.
-export const APP_VERSION = '1.3.1';
+export const APP_VERSION = '1.3.2';