Add thread/unarchive to restore archived rollouts

[charley-oai]

Summary

• Adds a new thread/unarchive RPC to move archived thread rollouts back into the active sessions/ tree.

What changed

• Protocol
  • Adds thread/unarchive request/response types and wiring.
• Server
  • Implements thread_unarchive in the app server.
  • Validates the archived rollout path and thread ID.
  • Restores the rollout to sessions/YYYY/MM/DD/... based on the rollout filename timestamp.
• Core
  • Adds find_archived_thread_path_by_id_str helper for archived rollouts.
• Docs
  • Documents the new RPC and usage example.
• Tests
  • Adds an end-to-end server test that:
    1. starts a thread,
    2. archives it,
    3. unarchives it,
    4. asserts the file is restored to sessions/.

How to use

{ "method": "thread/unarchive", "id": 24, "params": { "threadId": "<thread-id>" } }

Author Codex Session

codex resume 019bf158-54b6-7960-a696-9d85df7e1bc1 (soon I'll make this kind of session UUID forkable by anyone with the right session_object_storage_url line in their config, but for now just pasting it here for my reference)

[charley-oai]

@codex review this

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. What shall we delve into next?

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