fix(linear): match angle-bracket autolink URL form in attachment/image scan (ABCA-744)

Live-caught on ABCA-744: Linear normalizes a plain `[f](https://…)` link
into the CommonMark autolink form `[f](<https://…>)` on round-trip. The
un-bracketed pattern didn't match, so the uploads.linear.app attachment was
silently dropped — the task ran without it, no error.

Fix both scan patterns to accept optional `<`/`>` around the URL and
exclude `>` from the URL body:
- linear-attachments.MARKDOWN_LINK_OR_IMAGE_PATTERN (authenticated fetch)
- linear-webhook-processor.extractImageUrlAttachments (public-CDN image path)

Adds a regression test asserting the angle-bracket form is matched and the
captured URL excludes the trailing '>'.

Author: isadeks

cdk/src/handlers/linear-webhook-processor.ts

@@ -3210,7 +3210,10 @@ async function screenCommentsOrDrop(
 function extractImageUrlAttachments(description: string | undefined): Attachment[] {
   if (!description) return [];
 
-  const imagePattern = /!\[[^\]]*\]\((https:\/\/[^)]+)\)/g;
+  // Angle-bracket URL form `![alt](<https://…>)` is the CommonMark autolink
+  // Linear normalizes links into (see linear-attachments.MARKDOWN_LINK_OR_IMAGE_PATTERN,
+  // ABCA-744). Optional `<`/`>`, excluded from the capture.
+  const imagePattern = /!\[[^\]]*\]\(<?(https:\/\/[^)>]+)>?\)/g;
   const attachments: Attachment[] = [];
   let skippedLinearUploads = 0;
   let match: RegExpExecArray | null;

cdk/src/handlers/shared/linear-attachments.ts

@@ -80,11 +80,16 @@ const PDF_MAGIC = [0x25, 0x50, 0x44, 0x46, 0x2d] as const; // %PDF-
  * Markdown reference to a `uploads.linear.app` file. Matches BOTH the image form
  * `![alt](url)` AND the plain link form `[label](url)` — Linear embeds uploaded
  * images inline (`!`) but attaches uploaded files (PDFs, logs, specs) as plain
- * links. The leading `!` is optional so both are captured. Mirrors the image
- * pattern in `linear-webhook-processor.extractImageUrlAttachments` (which only
- * needs the `!` form for the public-CDN URL path).
+ * links. The leading `!` is optional so both are captured.
+ *
+ * The URL may be wrapped in angle brackets — `[label](<https://…>)` — which is
+ * the CommonMark autolink form Linear NORMALIZES uploaded-file links into (live-
+ * caught on ABCA-744: a plain `[f](https://…)` link round-tripped through Linear
+ * comes back as `(<https://…>)`, and the un-bracketed pattern silently dropped
+ * it). The `<`/`>` are optional and excluded from the captured URL, and `>` is
+ * excluded from the URL body so the closing bracket can't leak in.
  */
-const MARKDOWN_LINK_OR_IMAGE_PATTERN = /!?\[[^\]]*\]\((https:\/\/[^)]+)\)/g;
+const MARKDOWN_LINK_OR_IMAGE_PATTERN = /!?\[[^\]]*\]\(<?(https:\/\/[^)>]+)>?\)/g;
 
 /** Extension → MIME for typing a Linear upload when the response content-type
  *  is generic (e.g. application/octet-stream). Only platform-allowed types. */

cdk/test/handlers/shared/linear-attachments.test.ts

@@ -220,6 +220,21 @@ describe('downloadScreenAndStoreLinearAttachments', () => {
     expect(putSendMock).toHaveBeenCalledTimes(1);
   });
 
+  test('matches the angle-bracket autolink URL form Linear normalizes links into (ABCA-744)', async () => {
+    // Linear round-trips `[f](https://…)` into `[f](<https://…>)`. The un-bracketed
+    // pattern dropped it silently (live-caught on ABCA-744) — the attachment
+    // never reached S3 and the task ran without it.
+    (global.fetch as jest.Mock).mockResolvedValueOnce(bytesResponse(PDF_BYTES, 200, 'application/pdf'));
+    const desc = 'See [design.pdf](<https://uploads.linear.app/u/p/design.pdf>) attached.';
+    const records = await downloadScreenAndStoreLinearAttachments(desc, 10, storageCtx());
+    expect(records).toHaveLength(1);
+    expect(records[0].type).toBe('file');
+    expect(records[0].content_type).toBe('application/pdf');
+    // The captured URL must NOT include the trailing '>' (the fetch must hit the real URL).
+    const fetchedUrl = (global.fetch as jest.Mock).mock.calls[0][0] as string;
+    expect(fetchedUrl).toBe('https://uploads.linear.app/u/p/design.pdf');
+  });
+
   test('types a generic octet-stream response by its .log extension and screens as text', async () => {
     (global.fetch as jest.Mock).mockResolvedValueOnce(bytesResponse(TEXT_BYTES, 200, 'application/octet-stream'));
     const records = await downloadScreenAndStoreLinearAttachments(