Clarify MCP clients and local-model setup

[VelizarSeleznev]

Summary

• separate client setup from model-provider setup: OpenCode does not require LM Studio, and direct LM Studio does not require OpenCode
• document the common OpenCode + LM Studio path as an optional combination
• add a manual direct-LM-Studio path suitable for local models
• document Antigravity setup and the distinction between normal interactive agy execution and the currently unreliable agy -p mode
• align setup examples with explicit --project binding and the complete MCP registry

Verification

• npm run check
• 0 errors; 3 existing orphan-page warnings
• git diff --check origin/main

Coordination

The commands described here target the canonical 2.8 MCP package PR. Keep this draft until that npm release is available.