Enforce Effect-native lint policy

[K-Mistele]

Summary

• vendor reviewed anti-slop and TypeOnce Oxlint rules at pinned upstream revisions and enable the compatible Fold policy
• migrate every switch to Effect Match, replace executable runtime classifiers with Effect predicates/tag guards, and use Effect-native recovery, clock, and ignore combinators
• keep focused platform-boundary exceptions while enforcing the required conditional-spread, symbol-name, and no-switch rules repository-wide

Validation

• bun run typecheck
• bun run lint
• bun run format:check
• bun run test (676 passed, 14 terminal-control tests skipped by default)
• git diff --check
• structural audits report no executable instanceof, runtime typeof, or property in expressions under packages/ and scripts/