perf(contracts): optimize agent config change comparisons

[Yevanchen]

Summary

• Optimize agent config change classification by comparing ordered MCP server and skill arrays directly.
• Add regression coverage that order changes remain visible for MCP bindings and skills.

Why

• The complexity scan flagged repeated nested work in config change classification.
• These arrays have stable ordered string fields, so linear comparison avoids full stable JSON serialization while preserving existing order-sensitive behavior.

Verification

• Commands:
  • vp exec bun test apps/api/tests/agent-versioned-config-plan.test.ts
  • vp fmt --check pkgs/contracts/src/agent/agent-config-change-plan.contract.ts apps/api/tests/agent-versioned-config-plan.test.ts
  • vp run --filter @mosoo/contracts tc
  • vp run --filter @mosoo/contracts test
• Manual steps: N/A
• Not run: Full workspace vp run -w check

Impact

• User/API/contract changes: No public contract shape changes; internal classification remains order-sensitive.
• Generated files / GraphQL / DB / lockfile: N/A
• Env or config changes: N/A
• Risk and rollback: Low; rollback is reverting the single commit.

Review

• Closest review areas: pkgs/contracts/src/agent/agent-config-change-plan.contract.ts, apps/api/tests/agent-versioned-config-plan.test.ts
• Known trade-offs: Provider options and built-in tools still use stable serialization because nested object key order must remain normalized.