Restore scoped formatting and static-analysis CI gates

[stakach]

Migrated roadmap scope. Historical context: completion ledger.

Dependencies: #4.

Acceptance

• Inventory existing fmt/clippy debt without making unrelated formatting churn part of functional PRs.
• Resolve warnings and formatting incrementally in focused owners, then enable meaningful gates.
• Keep crate specs independently runnable and never hide a test failure behind lint configuration.

Track progress and verification here and in PRs. Host specs, native builds and end-to-end proof are distinct; retire superseded machinery at its actual cutover.