Blob paste and clone always fail on emulator connections

Problem

Blob paste and clone fail 100% of the time on emulator connections. The SAS builder requests the optional t (tag) permission, but emulator SAS is pinned to service version 2018-03-28, which predates that permission. The result is a client-side RangeError -- Azurite is never contacted.

Container-level paste is already gated for emulator connections, but blob-level paste is not, so the UI offers an action that cannot succeed.

Evidence

• PasteBlobs.ts:228 -- requests optional t, branching on connection type rather than on whether the target is the emulator
• blob-extension/src/index.ts:520-522 -- pins emulatorApiVersion (defined line 118) to 2018-03-28
• blob-extension/src/index.ts:650-657 -- the existing container-level gate, canPasteBlobContainerToBlobContainersNode, which has no blob-level equivalent

Suggested fix

Either omit the t permission when the target is the emulator, or extend the existing gate to blob-level paste so the action is not offered.

Found while automating the blob paste E2E cases.

Start with PasteBlobs.ts:228 and compare its emulator handling with blob-extension/src/index.ts:650-657, using emulatorApiVersion at line 118 as context. Run the blob paste E2E cases mentioned in the issue. Done means blob paste and clone no longer fail on emulator connections and the UI does not offer an action that cannot succeed.