fix(media): parse local file extensions across path styles (#105614)

* fix(media): parse local file extensions across path styles

* docs: note cross-platform media path fix

* docs: keep release notes in PR context

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

packages/media-core/src/mime.test.ts

@@ -209,6 +209,8 @@ describe("getFileExtension", () => {
     { filePath: "https://cdn.example.com/bad%ZZ%2Emp4", expected: undefined },
     { filePath: "https://cdn.example.com/render%2Emp4/", expected: undefined },
     { filePath: String.raw`C:\media\clip.MP4`, expected: ".mp4" },
+    { filePath: String.raw`C:\media.folder\clip`, expected: undefined },
+    { filePath: String.raw`C:\media.folder\clip.MP4`, expected: ".mp4" },
   ] as const)("extracts $expected from $filePath", ({ filePath, expected }) => {
     expect(getFileExtension(filePath)).toBe(expected);
   });

packages/media-core/src/mime.ts

@@ -1,6 +1,7 @@
 // Media Core module implements mime behavior.
 import path from "node:path";
 import { type MediaKind, mediaKindFromMime } from "./constants.js";
+import { extnameFromAnyPath } from "./file-name.js";
 import { createLazyImportLoader } from "./lazy-import.js";
 
 /** Maximum byte prefix passed to dependency MIME sniffers for bounded memory/CPU work. */
@@ -157,7 +158,7 @@ export function getFileExtension(filePath?: string | null): string | undefined {
   } catch {
     // fall back to plain path parsing
   }
-  const ext = path.extname(filePath).toLowerCase();
+  const ext = extnameFromAnyPath(filePath).toLowerCase();
   return ext || undefined;
 }