v0.6.0-rc87

Add final mermaid validation to ProbeAgent SDK mode (#166)

Fix missing mermaid validation in SDK mode by adding final validation
step before returning results. This ensures parity with CLI mode which
already validates all mermaid diagrams regardless of schema context.

Fixes issue where mermaid diagrams with special characters like
<CHORUS_TAG> were not being auto-corrected when using probe agent
through SDK/visor integration.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>