feat(web): add search to Rules page

Filter sections by typing in the search box — matches against both
section titles and content. Shows result count and a "no results"
message. Expand/Collapse All buttons respect the filtered set.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/index.css

@@ -542,12 +542,34 @@ button:disabled {
 }
 
 /* Rules Page */
+.rules-search {
+  width: 100%;
+  padding: var(--spacing-sm) var(--spacing-md);
+  margin-bottom: var(--spacing-sm);
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius);
+  background: var(--color-surface);
+  color: var(--color-text);
+  font-size: 1rem;
+}
+
+.rules-search::placeholder {
+  color: var(--color-text-muted);
+}
+
 .rules-actions {
   display: flex;
+  align-items: center;
   gap: var(--spacing-sm);
   margin-bottom: var(--spacing-md);
 }
 
+.rules-count {
+  font-size: 0.85rem;
+  color: var(--color-text-muted);
+  margin-left: auto;
+}
+
 .rules-sections {
   display: flex;
   flex-direction: column;

web/src/pages/RulesPage.tsx

@@ -1,4 +1,4 @@
-import { useState } from 'react';
+import { useState, useMemo } from 'react';
 import Markdown from 'react-markdown';
 import remarkGfm from 'remark-gfm';
 import TopBar from '../components/layout/TopBar';
@@ -7,6 +7,15 @@ import { battleReferenceSections } from '../rules/battle-reference';
 
 export default function RulesPage() {
   const [openSections, setOpenSections] = useState<Set<number>>(new Set());
+  const [search, setSearch] = useState('');
+
+  const filtered = useMemo(() => {
+    if (!search.trim()) return battleReferenceSections.map((s, i) => ({ ...s, originalIndex: i }));
+    const q = search.toLowerCase();
+    return battleReferenceSections
+      .map((s, i) => ({ ...s, originalIndex: i }))
+      .filter((s) => s.title.toLowerCase().includes(q) || s.content.toLowerCase().includes(q));
+  }, [search]);
 
   const toggle = (index: number) => {
     setOpenSections((prev) => {
@@ -21,7 +30,7 @@ export default function RulesPage() {
   };
 
   const expandAll = () => {
-    setOpenSections(new Set(battleReferenceSections.map((_, i) => i)));
+    setOpenSections(new Set(filtered.map((s) => s.originalIndex)));
   };
 
   const collapseAll = () => {
@@ -32,6 +41,14 @@ export default function RulesPage() {
     <>
       <TopBar title="Ship Reference" />
       <PageContainer>
+        <input
+          type="search"
+          className="rules-search"
+          placeholder="Search rules..."
+          value={search}
+          onChange={(e) => setSearch(e.target.value)}
+        />
+
         <div className="rules-actions">
           <button className="btn-secondary btn-sm" onClick={expandAll}>
             Expand All
@@ -39,12 +56,15 @@ export default function RulesPage() {
           <button className="btn-secondary btn-sm" onClick={collapseAll}>
             Collapse All
           </button>
+          {search.trim() && (
+            <span className="rules-count">{filtered.length} result{filtered.length !== 1 ? 's' : ''}</span>
+          )}
         </div>
 
         <div className="rules-sections">
-          {battleReferenceSections.map((section, i) => (
-            <details key={i} className="rules-section" open={openSections.has(i)}>
-              <summary className="rules-summary" onClick={(e) => { e.preventDefault(); toggle(i); }}>
+          {filtered.map((section) => (
+            <details key={section.originalIndex} className="rules-section" open={openSections.has(section.originalIndex)}>
+              <summary className="rules-summary" onClick={(e) => { e.preventDefault(); toggle(section.originalIndex); }}>
                 {section.title}
               </summary>
               <div className="rules-content">
@@ -59,6 +79,11 @@ export default function RulesPage() {
               </div>
             </details>
           ))}
+          {filtered.length === 0 && (
+            <p className="empty-text" style={{ padding: 'var(--spacing-md) 0' }}>
+              No sections match "{search}".
+            </p>
+          )}
         </div>
       </PageContainer>
     </>