[codex] Migrate thread turns list to thread store

[wiltzius-openai]

• Migrate thread/turns/list history loading to ThreadStore::read_thread(... include_history: true ...), with loaded-thread fallback through live thread history.
• Preserve active turn merging and existing pagination/cursor behavior while removing direct rollout path resolution from the endpoint.
• Keep v2 thread/list pathless-store friendly by converting StoredThread directly to API Thread, and add regression coverage for pathless store history/listing.

[chatgpt-codex-connector]

💡 Codex Review

codex/codex-rs/app-server/src/codex_message_processor.rs

Lines 4915 to 4922 in 6addbab

	let result = if let Some(path) = path {
	self.thread_store
	.read_thread_by_rollout_path(StoreReadThreadByRolloutPathParams {
	rollout_path: path.clone(),
	include_archived: true,
	include_history,
	})
	.await

Keep path-based fork/resume working with remote thread stores

thread/resume and thread/fork are documented to accept path, but this helper now routes every path-based request through ThreadStore::read_thread_by_rollout_path(). RemoteThreadStore hard-fails that method, so enabling experimental_thread_store_endpoint turns valid path-based requests into internal errors instead of loading the local rollout as before.

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