docs(middleware): spec (amended) + Plan A (py rename) + Plan B (js package) (#666)

Spec amended for repo reality: JS package lives at libs/middleware built with
@nx/js:tsc/@nx/vitest (no tsup in repo), mirroring libs/telemetry; API
signatures reconciled to the Python source (serverToolNames params).

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: blove