Enhance file download handling and web interface. Update the download handler to support inline previews based on query parameters. Introduce a preview button for supported file types in the web interface, along with corresponding styles for action buttons. This improves user experience by allowing direct file previews without downloads.

lib/agent/web/app.js

@@ -61,6 +61,20 @@
     return `${value.toFixed(value >= 10 ? 0 : 1)} ${units[i]}`;
   }
 
+  // ponytail: extension allowlist; browsers that can't render still get a tab (download/blank)
+  const previewExt = new Set([
+    "png", "jpg", "jpeg", "gif", "webp", "svg", "bmp", "ico",
+    "pdf",
+    "txt", "log", "csv", "json", "xml", "html", "htm", "css", "js", "md",
+    "mp4", "webm", "ogg", "mp3", "wav",
+  ]);
+
+  function isPreviewable(filename) {
+    const i = String(filename).lastIndexOf(".");
+    if (i < 0) return false;
+    return previewExt.has(String(filename).slice(i + 1).toLowerCase());
+  }
+
   function joinPath(base, name) {
     if (!base) return name;
     if (/[\\/]$/.test(base)) return base + name;
@@ -178,15 +192,27 @@
       const modified = document.createElement("td");
       modified.textContent = entry.modified_time ? new Date(entry.modified_time).toLocaleString() : "";
       const action = document.createElement("td");
+      action.className = "actions";
+      const full = joinPath(data.path, entry.name);
       const del = document.createElement("button");
       del.type = "button";
       del.textContent = "Delete";
-      const full = joinPath(data.path, entry.name);
       del.addEventListener("click", (event) => {
         event.stopPropagation();
         deleteFile(full, entry.name).catch((err) => showError(err.message));
       });
       action.append(del);
+      if (entry.type === "file" && isPreviewable(entry.name)) {
+        const preview = document.createElement("button");
+        preview.type = "button";
+        preview.textContent = "Preview";
+        preview.addEventListener("click", (event) => {
+          event.stopPropagation();
+          const url = `/api/v1/download?path=${encodeURIComponent(full)}&inline=1`;
+          window.open(url, "_blank", "noopener");
+        });
+        action.append(preview);
+      }
       tr.append(name, type, size, modified, action);
       fileRows.append(tr);
     }