Slice 13: repo search + filtering (+ no-cache dev assets)

<repo-list> gains a search box (name/path) and Dirty/Ahead-behind filter chips with an N-of-M count; filtering is client-side and the state persists in localStorage (gitmanager.repolist.filters, §4). Refresh/selection re-apply filters. cmd/server sends Cache-Control: no-cache for /components and /static so hot-reloaded asset edits show on reload. Server-verified (curl); live click-through pending an unresponsive browser pane.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/templates/help.html

@@ -38,6 +38,14 @@
       <li>Run <code>docker compose up</code> and open the dashboard.</li>
     </ol>
 
+    <h2>Finding a repository</h2>
+    <p>
+      Use the search box above the list to filter by name or path, and the
+      <strong>Dirty</strong> and <strong>Ahead/behind</strong> chips to show only
+      repos with uncommitted changes or commits to sync. The count shows how many
+      match. Your search and filters are remembered on this device.
+    </p>
+
     <h2>Reading the dashboard</h2>
     <ul>
       <li><strong>Branch</strong> — the checked-out branch (or <code>HEAD</code> when detached).</li>