fix: msteams attachments + plugin prompt hints

Co-authored-by: Christof <10854026+Evizero@users.noreply.github.com>

extensions/msteams/src/media-helpers.ts

@@ -0,0 +1,77 @@
+/**
+ * MIME type detection and filename extraction for MSTeams media attachments.
+ */
+
+import path from "node:path";
+
+import {
+  detectMime,
+  extensionForMime,
+  extractOriginalFilename,
+  getFileExtension,
+} from "clawdbot/plugin-sdk";
+
+/**
+ * Detect MIME type from URL extension or data URL.
+ * Uses shared MIME detection for consistency with core handling.
+ */
+export async function getMimeType(url: string): Promise<string> {
+  // Handle data URLs: data:image/png;base64,...
+  if (url.startsWith("data:")) {
+    const match = url.match(/^data:([^;,]+)/);
+    if (match?.[1]) return match[1];
+  }
+
+  // Use shared MIME detection (extension-based for URLs)
+  const detected = await detectMime({ filePath: url });
+  return detected ?? "application/octet-stream";
+}
+
+/**
+ * Extract filename from URL or local path.
+ * For local paths, extracts original filename if stored with embedded name pattern.
+ * Falls back to deriving the extension from MIME type when no extension present.
+ */
+export async function extractFilename(url: string): Promise<string> {
+  // Handle data URLs: derive extension from MIME
+  if (url.startsWith("data:")) {
+    const mime = await getMimeType(url);
+    const ext = extensionForMime(mime) ?? ".bin";
+    const prefix = mime.startsWith("image/") ? "image" : "file";
+    return `${prefix}${ext}`;
+  }
+
+  // Try to extract from URL pathname
+  try {
+    const pathname = new URL(url).pathname;
+    const basename = path.basename(pathname);
+    const existingExt = getFileExtension(pathname);
+    if (basename && existingExt) return basename;
+    // No extension in URL, derive from MIME
+    const mime = await getMimeType(url);
+    const ext = extensionForMime(mime) ?? ".bin";
+    const prefix = mime.startsWith("image/") ? "image" : "file";
+    return basename ? `${basename}${ext}` : `${prefix}${ext}`;
+  } catch {
+    // Local paths - use extractOriginalFilename to extract embedded original name
+    return extractOriginalFilename(url);
+  }
+}
+
+/**
+ * Check if a URL refers to a local file path.
+ */
+export function isLocalPath(url: string): boolean {
+  return url.startsWith("file://") || url.startsWith("/") || url.startsWith("~");
+}
+
+/**
+ * Extract the message ID from a Bot Framework response.
+ */
+export function extractMessageId(response: unknown): string | null {
+  if (!response || typeof response !== "object") return null;
+  if (!("id" in response)) return null;
+  const { id } = response as { id?: unknown };
+  if (typeof id !== "string" || !id) return null;
+  return id;
+}