fix: make build pass and retain completed todos

[jaesbit]

Summary

• externalize mupdf from the Bun server bundle so the production build handles its top-level await dependency
• keep the last todo list visible, including completed checks, after the SDK auto-clear event
• derive todo snapshots from persisted session entries so reconnects retain the completed list until a new todo_write replaces it

Verification

• bun run build
• bun run --filter '@omp-deck/server' typecheck
• cd apps/server && bun test src/bridge/in-process-queue.test.ts
• cd apps/web && bun test src/lib/reducer.test.ts