RFC: Skills Observability via Client Hooks

This RFC proposes adding client hook management to ToolHive, enabling
OpenTelemetry-based observability for agent skill execution.

Key features:
- Client shim architecture to normalize different hook formats
- Primary support for Claude Code and Cursor
- Standalone mode (transitional) and server-managed mode (target)
- Enterprise deployment via config file + server auto-start
- Integration with THV-0034 long-running server architecture

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: JAORMX