Bump version to 0.6.0 (Phase 6 milestone)

[vicmaster]

Summary

Phase 6 (Evaluation & AI Loops) is complete. Bumps package.json and the McpServer version string from 0.5.0 to 0.6.0 to match the roadmap label.

What Phase 6 shipped

Across 3 PRs:

• Phase 6b: benchmark suite for canvas_evaluate scoring stability #17 Benchmark suite — benchmark/corpus/{hero,minimal,bad-contrast}.ts, baselines.json, drift-detecting runner, npm run bench.
• Phase 6c: canvas_autofix — mechanical fixes as batch_design ops #18 canvas_autofix — mechanical fixes (spacing scale snap, missing layout → vertical, WCAG contrast → #000/#FFF) emitted as ready-to-run batch_design ops.
• Phase 6a: LLM-as-judge mode for canvas_evaluate #19 LLM-judge mode — pluggable provider table (Anthropic + OpenAI), canvas_evaluate({mode: "llm"}) adds an llmCritique field with score / summary / strengths / weaknesses / suggestions.

After merge: tag v0.6.0 and create the matching GitHub release.