feat: add gameplay assists and variant generator

src/components/HelpDialog.tsx

@@ -11,12 +11,13 @@ export function HelpDialog({
     <Modal open={open} title="Sudoku Tools help" onClose={onClose} wide>
       <div className="help-grid">
         <section>
-          <h3>Four complementary workspaces</h3>
+          <h3>Five complementary workspaces</h3>
           <p>
             <strong>Play</strong> keeps values, two kinds of notes, colours,
             history and elapsed time. <strong>Set</strong> edits clues and
-            constraints. <strong>Solve</strong> explains logical steps and can
-            verify uniqueness. <strong>Helpers</strong> answers focused
+            constraints. <strong>Generate</strong> constructs and rates bounded,
+            seedable variants. <strong>Solve</strong> explains logical steps and
+            can verify uniqueness. <strong>Helpers</strong> answers focused
             questions without changing the board.
           </p>
         </section>
@@ -47,6 +48,10 @@ export function HelpDialog({
               <dt>Ctrl/⌘ + Z/Y</dt>
               <dd>Undo or redo</dd>
             </div>
+            <div>
+              <dt>Ctrl/⌘ + click</dt>
+              <dd>Highlight every placed copy of that digit</dd>
+            </div>
           </dl>
         </section>
         <section>
@@ -59,6 +64,16 @@ export function HelpDialog({
             explanation.
           </p>
         </section>
+        <section>
+          <h3>Generation and ratings</h3>
+          <p>
+            Generation runs in a worker with explicit time and search limits. A
+            requested level guides clue removal; the reported rating is then
+            calculated independently from logical techniques, clue load and
+            bounded exact-search evidence. A limit never becomes a false
+            uniqueness claim.
+          </p>
+        </section>
         <section>
           <h3>Import and privacy</h3>
           <p>