feat(live): add managed primary WebSocket connections (#1095)

Java's Live REST resources and event types are available, but callers
cannot open a managed primary Live WebSocket. Add an optional
`LiveConnection` over the existing authenticated transport. Connecting
opens the socket only; callers send the generated session.start command
and observe session.started. A caller that sends session.close can drain
errors, transcripts and final usage on the same receive path through
session.closed before closing the transport.

This is primary support only; fork and sideband require separate review
units. The change contains three handwritten helper/options/test files,
with no generated model or service changes.

Validation:
- Native Gradle: 42/42 passed (14 Live, 13 GA Realtime, 15 Responses
lifecycle).
- Reproduced and fixed single-thread callback reads, custom transports
joining their reader at close, and throwing cleanup after a retired
handshake.
- Repository ktfmt 0.61 checks passed; trusted 80530c6 custom-code
budget 2998/3000 and isolation passed.
- Compiled new public API bytecode version 52 (Java 8) and checked its
typed overloads. Hosted Java 8/25, older Jackson, and compatibility CI
remain pending.

Author: markstuart-oai