Add Insight storage projection foundation

[josiahking]

Summary

• add primitive-only diagnostic batch snapshots and projection
• add a minimal diagnostic batch store contract and in-memory implementation
• add a sink adapter that projects finalized batches into storage snapshots
• update Insight documentation and repository source-inventory expectations

Validation

• package, architecture, documentation and root quality checks passed
• release-package and supply-chain validation passed
• deterministic package split validation passed
• prerelease consumer validation passed
• application skeleton create-project validation passed

Persistent storage, retention, redaction, filtering, sampling, watchers and runtime composition remain outside this change.