internal/mcpclient speaks streamable HTTP: initializes once and keeps
the session the server gives, beginning it again once if the server
forgot it; lists tools page by page; calls one with headers of its own,
taking the answer as JSON or as events with progress before it; and
bounds what it reads. mcptest is a server for tests.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
