[codex] improve vbi test coverage

[youngwinds]

Summary

• add focused internal tests for VBI chart/report/insight helpers, resource stores, date predicate resolution, and utility export paths
• cover report snapshot, schema lookup, UUID guards, and collection helper branches that were previously untested
• update the root coverage badge after raising @visactor/vbi coverage to about 99.31% statements/lines and 94.13% branches

Why

The existing VBI test suite covered the main builder flows well, but several small internal modules and boundary branches were still untested. This change fills those gaps without spending effort on low-value defensive branches or type-only barrel files.

Impact

• higher confidence in VBI internal helpers and builder edge cases
• stronger regression protection for report/resource wiring and date filter predicate logic
• repository README now reflects the latest VBI coverage badge

Validation

• pnpm --filter @visactor/vbi run test
• pnpm --filter @visactor/vbi run test:coverage
• pnpm --filter @visactor/vbi run typecheck
• pre-push hook: pnpm turbo typecheck