dashboard: drop the path-link and side-panel code the flow page was the only user of

appendLinkified had one caller, the flow page, and it pulled in the
path-link and file-preview chain, the side-panel singleton, the marked
and DOMPurify wiring and the css only they used. The docs stop
describing the dashboard side panel and the client reading file_refs.

frontend/packages/dashboard/src/index.html

@@ -240,12 +240,6 @@
       <p class="meta" id="hive-rev" hidden></p>
     </footer>
 
-    <!-- Slide-in detail panel (clicked file previews, applied config)
-       is a <hive-side-panel> element
-       (@hive/shared/side-panel.js) — the Panel singleton in common.js
-       creates + appends it to <body> lazily on first use, so nothing
-       needs to be pre-declared here. -->
-
     <!-- Selection action bar. Sticky-bottom strip that slides into
        view when one or more agent cards is selected (click the icon
        to toggle). See docs/web-ui/dashboard.md::Selection bar for the bulk
@@ -272,8 +266,7 @@
 
     <!-- Single bundled entry — tabs.js is the dashboard tabs surface;
        esbuild folds
-       @hive/shared/terminal.js and the marked npm package into
-       tabs.js. -->
+       @hive/shared/terminal.js into tabs.js. -->
     <script type="module" src="/static/tabs.js" defer></script>
   </body>
 </html>