Blob paste swallows setup errors and reports success

Problem

pasteBlobsWithoutPrompt returns Promise<void> and swallows every setup error. The catch block logs to the activity log and then returns normally, so the caller cannot distinguish three very different outcomes: the paste succeeded, the user cancelled, or setup failed outright.

ErrorInsufficientCredentials routes through that same catch, so this is not emulator-only -- real Azure connections are affected. A user who lacks permission to read the source sees the operation appear to complete.

Evidence

• PasteBlobs.ts:125-129 -- catch logs and returns
• PasteBlobs.ts:43 -- signature is Promise<void>
• index.ts:116 -- provider AzCopy.Blob.pasteBlobs returns it directly to the caller

Suggested fix

Return a discriminated result (succeeded / cancelled / failed) so callers can react, and let genuine setup failures surface to the user rather than resolving silently.

Found while automating the blob paste E2E cases.

Start with PasteBlobs.ts at the Promise signature and catch block, then inspect index.ts:116 to understand how the provider result reaches callers. Use the blob paste E2E cases mentioned in the issue to verify that success, cancellation, and setup failure are distinguishable, with genuine setup errors no longer reported as successful completion.