refactor(knowledge): reuse existing getMimeTypeFromExtension from uploads

Replace duplicate EXTENSION_MIME_MAP and getMimeTypeFromExtension with
the existing, more comprehensive version from lib/uploads/utils/file-utils.

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

Author: waleedlatif1

apps/sim/tools/knowledge/types.ts

@@ -1,34 +1,24 @@
-const EXTENSION_MIME_MAP: Record<string, string> = {
-  html: 'text/html',
-  htm: 'text/html',
-  md: 'text/markdown',
-  csv: 'text/csv',
-  json: 'application/json',
-  yaml: 'application/x-yaml',
-  yml: 'application/x-yaml',
-  xml: 'application/xml',
-  txt: 'text/plain',
-} as const
-
-/**
- * Infers MIME type from a file extension. Returns `text/plain` for unknown extensions.
- */
-export function getMimeTypeFromExtension(ext: string): string {
-  return EXTENSION_MIME_MAP[ext.toLowerCase()] ?? 'text/plain'
-}
+import {
+  getFileExtension,
+  getMimeTypeFromExtension as getUploadMimeType,
+} from '@/lib/uploads/utils/file-utils'
 
 /**
  * Extracts extension from a filename and returns the normalized filename and MIME type.
  * If no extension is present, appends `.txt` and uses `text/plain`.
+ * Falls back to `text/plain` for unknown extensions (knowledge docs are always text content).
  */
 export function inferDocumentFileInfo(documentName: string): {
   filename: string
   mimeType: string
 } {
-  const dotIndex = documentName.lastIndexOf('.')
-  if (dotIndex > 0) {
-    const ext = documentName.slice(dotIndex + 1).toLowerCase()
-    return { filename: documentName, mimeType: getMimeTypeFromExtension(ext) }
+  const ext = getFileExtension(documentName)
+  if (ext) {
+    const mimeType = getUploadMimeType(ext)
+    return {
+      filename: documentName,
+      mimeType: mimeType === 'application/octet-stream' ? 'text/plain' : mimeType,
+    }
   }
   return { filename: `${documentName}.txt`, mimeType: 'text/plain' }
 }