refactor(bayn): remove duplicate paper episode lifecycle

[gregkonush]

Summary

• remove the unused in-memory PaperEpisodeState reducer that never controlled production execution
• retain the pure grant, allocation, authority, close-window, and durable-cycle terminalization decisions used by Bayn
• remove tests for the parallel lifecycle while preserving behavioral coverage of the canonical durable lifecycle

Related Issues

None

Testing

• bun test services/bayn/src/paper-episode.test.ts services/bayn/src/composition.test.ts services/bayn/src/observe-composition.test.ts (69 passed)
• bun run --filter @proompteng/bayn tsc
• bun run --filter @proompteng/bayn lint:effect
• git diff --check

Breaking Changes

None. The removed symbols had no production consumers.

Checklist

• Testing section documents the exact validation performed (or N/A with justification).
• Screenshots and Breaking Changes sections are handled appropriately (removed or filled in).
• Documentation, release notes, and follow-ups are updated or tracked.

[gregkonush]