fix(a11y): add accessible names to hud sliders and inputs

Add explicit aria-label attributes to unlabelled interactive controls in index.html and dynamic parameter sliders in src/ui.js, fulfilling WCAG 2.1 Success Criterion 4.1.2 (Name, Role, Value).

- Add aria-label to #scope-feather-slider, #bloom-intensity-slider, #sharpen-intensity-slider, #location-search, #scene-import-file, and first-run suppression checkbox.
- Set aria-label to uniform label on dynamic style parameter sliders in ui.js.
- Add unit test suite (src/hudA11y.test.mjs) verifying accessible names across all inputs in index.html and dynamic slider construction.

Signed-off-by: Kushagra Kumar <[email protected]>

index.html

@@ -440,7 +440,7 @@
              mirrors SCOPE_FEATHER_RATIO_DEFAULT in src/scopeMask.js. Feather
              softens the black mask edge; label fading is the separate Fade
              slider. -->
-        <input type="range" class="pp-slider" id="scope-feather-slider" min="0" max="100" value="11" title="Scope edge feather as a percentage of the keyhole radius" />
+        <input type="range" class="pp-slider" id="scope-feather-slider" min="0" max="100" value="11" aria-label="Scope edge feather" title="Scope edge feather as a percentage of the keyhole radius" />
         <span class="pp-slider-value" id="scope-feather-value">11%</span>
       </div>
     </div>
@@ -460,7 +460,7 @@
         <span class="pp-label">Bloom</span>
       </button>
       <div class="pp-slider-row" id="bloom-slider-row">
-        <input type="range" class="pp-slider" id="bloom-intensity-slider" min="0" max="200" value="0" />
+        <input type="range" class="pp-slider" id="bloom-intensity-slider" min="0" max="200" value="0" aria-label="Bloom intensity" />
         <span class="pp-slider-value" id="bloom-intensity-value">0%</span>
       </div>
     </div>
@@ -470,7 +470,7 @@
         <span class="pp-label">Sharpen</span>
       </button>
       <div class="pp-slider-row" id="sharpen-slider-row">
-        <input type="range" class="pp-slider" id="sharpen-intensity-slider" min="0" max="100" value="49" />
+        <input type="range" class="pp-slider" id="sharpen-intensity-slider" min="0" max="100" value="49" aria-label="Sharpen intensity" />
         <span class="pp-slider-value" id="sharpen-intensity-value">49%</span>
       </div>
     </div>
@@ -565,7 +565,7 @@
             <button id="search-toggle" class="search-toggle-btn" title="Search any location">
               <span>&#x1F50E;</span>
             </button>
-            <input type="text" id="location-search" placeholder="Search any location..." autocomplete="off" spellcheck="false" />
+            <input type="text" id="location-search" placeholder="Search any location..." autocomplete="off" spellcheck="false" aria-label="Search location by name or coordinates" />
           </div>
         </div>
       </div>
@@ -671,7 +671,7 @@
         <button id="scene-export-btn" class="scene-btn">EXPORT PRESETS</button>
         <button id="scene-import-btn" class="scene-btn">IMPORT</button>
         <button id="scene-download-btn" class="scene-btn">RUN LOG</button>
-        <input type="file" id="scene-import-file" accept="application/json,.json" hidden />
+        <input type="file" id="scene-import-file" accept="application/json,.json" hidden aria-label="Import scene JSON file" />
       </div>
       <div class="scene-progress">
         <div id="scene-progress-fill">0%</div>
@@ -872,7 +872,7 @@
     </div>
     <div class="first-run-footer">
       <label class="first-run-suppress">
-        <input type="checkbox" data-first-run-suppress />
+        <input type="checkbox" data-first-run-suppress aria-label="Do not show this message again on startup" />
         <span>Don't show this again</span>
       </label>
       <span>ESC to dismiss</span>