Paginated history projection breaks after a growing rollout provider rewrite

[Wangnov]

Summary

With the latest Codex paginated-history format, a cold rollout rewrite that grows the first JSONL line invalidates the persisted byte-offset checkpoint.

codex-threadripper sync reports success and the thread can still resume, but Codex can no longer project newly appended turns into thread_history_1.sqlite.

Verified environment

• Codex source: a30aee8d906c2ec4dfa07c794504d4ee7099f98a
• codex-threadripper: v0.3.5
• Isolated CODEX_HOME
• Thread explicitly created with historyMode: paginated

Reproduction

1. Create a paginated thread whose rollout provider is a short value such as L.
2. Let Codex project the existing rollout:
   • rollout size: 22241
   • projection checkpoint: byte offset 22241, ordinal 3
3. Make the rollout cold and run:
   codex-threadripper --provider openai sync
4. The first line grows by 261 bytes and the rollout size becomes 22502, while the projection checkpoint remains 22241|3.
5. Resume the thread and complete another turn.

Actual result

Codex logs projection failures:

expected value at line 1 column 1
expected ordinal 3, got 2

The runtime turn completes and is appended to the rollout, but it is not added to the paginated history projection.

Root cause

Codex now persists next_rollout_byte_offset in thread_history_1.sqlite. The cold rewrite path in src/rollout.rs replaces a shorter first line with a longer one, shifting every downstream byte offset without coordinating the projection checkpoint.

Acceptance criteria

• Paginated threads must never be left with a stale rollout byte-offset checkpoint.
• A provider sync that cannot safely preserve paginated history must fail closed for that thread instead of partially updating SQLite and rollout metadata.
• Legacy history keeps the existing cold rewrite behavior.
• In-place same-length rollout patches remain supported.
• Regression tests cover short-to-long provider sync for both legacy and paginated threads.
• cargo fmt --check, all Rust tests, and an end-to-end probe against the latest Codex pass.

[Wangnov]

已由 #25 修复，并随 v0.3.6 发布。三平台 Release candidate、正式 Release、npm、crates.io 与 Homebrew tap 均已验证通过。