Add queued transports (transferUserInfo + transferFile) to SundialKitConnectivity

[leogdion]

Epic: brightdigit/AtLeast#182

Add both queued WatchConnectivity transports end-to-end in Sources/SundialKitConnectivity. transferUserInfo is the queued dictionary transport; transferFile is the queued binary partner (encoded Data written to a temp file). One .queued SendOptions flag selects between them based on whether the message is BinaryMessagable.

⚠️ Adding methods to ConnectivitySession / ConnectivitySessionDelegate is a breaking protocol change — every conformer (observer, manager, test mocks in both packages) must implement them.

Tasks

• ConnectivitySession.swift — add func transferUserInfo(_ userInfo: ConnectivityMessage) and func transferFile(_ fileURL: URL, metadata: ConnectivityMessage?).
• WatchConnectivitySession+ConnectivitySession.swift — implement via session.transferUserInfo(_:) and session.transferFile(_:metadata:) (ignore returned transfer handles for now).
• WatchConnectivitySession+WCSessionDelegate.swift — add receive delegates:
  • didReceiveUserInfo: → forward as ConnectivityMessage.
  • didReceive file: WCSessionFile → read file.fileURL into Data synchronously (WC deletes the file once this returns), then forward Data + metadata.
• ConnectivitySessionDelegate.swift — add didReceiveUserInfo: and didReceiveFile fileData: Data, metadata:. The file method carries Data, not URL, by design (symmetry with sendMessageData, sidesteps file-lifetime).
• NeverConnectivitySession.swift — stub both as no-ops.
• ConnectivityDelegateHandling.swift — add handleUserInfoReceived(_:) + handleFileReceived(_:metadata:) requirements and bridge methods.
• SendOptions.swift — add static let queued (one flag; dict → userInfo, binary → file). Default behavior unchanged.
• MessageTransport.swift / ConnectivitySendResult.context — add .userInfo and .file cases for result reporting.
• Update test mocks to satisfy the new protocol members.

Notes

• File-lifetime gotcha: the received WCSessionFile is deleted as soon as didReceive file: returns — the synchronous read is mandatory.
• The binary type footer (BinaryMessageEncoder) is embedded in the Data, so transferFile metadata is not needed for type resolution — keep it optional (parity with sendMessageData).

Foundation for brightdigit/SundialKitStream routing and the Sundial example demo.

[leogdion]

Reopening to re-close as not planned — this was previously closed as completed, but the work was reverted.

The queued transports landed on the atleast-beta.6 branch but were then dropped: the branch was history-rewritten back to a clean release base (v2.0.0-alpha.3) plus connectivity fixes only — no transferUserInfo / transferFile / .queued / SendOptions.useApplicationContext. The pre-rewrite implementation is preserved at backup/atleast-beta.6-queued.

Reason: in AtLeast the queued transferUserInfo path dropped the Start command (WCFileStorage enumerateIncomingUserInfos … NSFileReadNoSuchFileError (ENOENT)); latest-desired-state messages are better served by updateApplicationContext, which self-heals via replay. See epic brightdigit/AtLeast#182.