[codex] Persist direct prompt user events in durable stream

[odysseus0]

What changed

• append a durable message_end user event for every direct prompt
• reserve event index 0 for that input and begin runtime output at index 1
• use appendEventOnce with a deterministic submission key so normal processing and crash reconciliation can both deliver the event safely
• cover Node end-to-end replay, Node recovery deduplication, and Cloudflare recovery projection

Root cause

Direct submissions wrote the user input to canonical session state, but only runtime-generated events were subscribed into the public durable event stream. @flue/react reconstructs history from that stream, so a refresh could recover the assistant response while permanently omitting the corresponding user prompt.

Fixes #307.

Validation

• pnpm --dir packages/runtime run build
• pnpm --dir packages/runtime run check:types
• pnpm --dir packages/runtime exec vitest run test/node-agent-coordinator.test.ts test/cloudflare-agent-coordinator.test.ts (57 passed, 1 skipped)
• Biome and Prettier checks for all changed files
• local Cloudflare Durable Object integration: a new user prompt and assistant response both reconstructed after a full browser refresh

[astrobot-houston]

Thanks for the contribution! We're closing this PR and moving the conversation to the issue: #368

We've moved to a model where bugs and feature proposals are discussed in issues/discussions before code review, so the community can help prioritize and shape the work. Your branch is linked from the new thread so the implementation isn't lost — please join us there to continue the conversation.

— astrobot 🤖