fix(copilot): report the fetched size on an unavailable image

The bytes are in hand by the time preparation fails, so quoting record.size back
recreated the contradictory placeholder the download-cap path already fixed: a
client-declared figure printed beside the real reason. Same defect, one line
below the one it was fixed in.

Author: waleedlatif1

apps/sim/lib/copilot/vfs/file-reader.test.ts

@@ -80,11 +80,13 @@ describe('readFileRecord', () => {
 
       fetchWorkspaceFileBuffer.mockResolvedValue(bomb)
 
-      const result = await readFileRecord(imageRecord('bomb.png', bomb.length))
+      // Recorded size deliberately disagrees with the real bytes: it is client-declared,
+      // so the placeholder must report what was actually fetched.
+      const result = await readFileRecord(imageRecord('bomb.png', 999_999))
 
       expect(result?.attachment).toBeUndefined()
       expect(result?.content).toContain('It is too large to decode safely.')
-      // The byte count must survive formatting — a sub-1KB bomb formatted without
+      // The byte count must survive formatting too — a sub-1KB bomb formatted without
       // `includeBytes` collapses to "0 Bytes" next to the real reason.
       expect(result?.content).toContain(`(${bomb.length} Bytes)`)
     },

apps/sim/lib/copilot/vfs/file-reader.ts

@@ -481,7 +481,13 @@ export async function readFileRecord(record: WorkspaceFileRecord): Promise<FileR
           if (!prepared.ok) {
             span.setAttribute(TraceAttr.CopilotVfsReadOutcome, CopilotVfsReadOutcome.ImageTooLarge)
             return {
-              content: readPlaceholder.imageUnavailable(record.name, record.size, prepared.reason),
+              // The fetched buffer, not `record.size`: the bytes are in hand by now,
+              // so there is no reason to quote the client-declared figure back.
+              content: readPlaceholder.imageUnavailable(
+                record.name,
+                fetched.buffer.length,
+                prepared.reason
+              ),
               totalLines: 1,
             }
           }