fix: reconcile single-node SNSD topology

[cxymds]

Pull Request

Description

Reconcile a single local path-based SNSD membership with the only v3 ServerInfo row, and consume the optional server_info_endpoint identity supplied by newer RustFS snapshots. Ambiguous multi-server payloads remain unresolved instead of being guessed.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• Performance improvement
• Test improvements
• Security fix

Testing

• Unit tests added/updated
• Manual testing completed

pnpm install --frozen-lockfile
pnpm type-check
pnpm lint
pnpm exec prettier --check lib/performance-data.ts tests/lib/performance-data.test.js
pnpm test:run

Checklist

• Code follows the project's style guidelines
• Self-review completed
• TypeScript types are properly defined
• All commit messages are in English (Conventional Commits)
• All existing tests pass
• No new dependencies added, or they are justified

Related Issues

Related to rustfs/rustfs#5870

Screenshots (if applicable)

N/A — this changes reconciliation data only; no visual markup or styling changed.

Additional Notes

The fallback is intentionally limited to exactly one local membership and exactly one reported server. Multi-server ambiguity continues to surface as incomplete topology.