feat: add conservative catalog summaries

[duck8823]

Summary

• generate versioned keyed exact, Bloom, and session summary metadata with conservative fallback
• reconcile immutable segment metadata into a derived Catalog cache without changing ledger authority
• add resumable full-ledger/cache validation and aggregate-only diagnostics
• validate canonical manifest, binding, parent and child facts with bounded allocation
• add migration 47 plus no-false-negative, tamper, pagination, privacy, and cap regressions

Validation

• go test ./... -count=1
• go vet ./...
• go tool golangci-lint run --timeout=5m
• focused race tests
• independent GPT-5.6 Sol review: APPROVE

Closes #1663