Add four new example servers demonstrating different SEP-2053 variant
patterns:
- model-optimized (same tools, different descriptions per LLM family)
- trading (API versioning with deprecation lifecycle)
- research (context budget management)
- Refactor the existing variants-http example into a GitHub-style server
with custom ranking.
Signed-off-by: Kurt Degiorgio <kdegiorgio@bloomberg.net>
