feat(app-server): always return limited thread history

[owenlin0]

Why

Whenever we return a thread's history (turns and items) over app-server, always return the limited form as specified by the rollout policy EventPersistenceMode::Limited, even if the thread was previously started with EventPersistenceMode::Extended.

We're finding it is quite unscalable to be returning the extended history, so let's apply the same filtering logic of the rollout policy when we load and return the thread's history.

What Changed

• Reuse the rollout persistence policy when reconstructing app-server ThreadItem history so only EventPersistenceMode::Limited rollout items are replayed into API turns.
• Route thread/read, thread/resume, thread/fork, thread/turns/list, and rollback responses through the same filtered app-server history projection.
• Keep live active turns intact when composing a response for a currently running thread.
• Update command execution coverage so persisted extended command events are excluded from returned history for thread/read, thread/fork, and thread/turns/list.

Test Plan

• cargo test -p codex-app-server limited
• cargo test -p codex-app-server thread_shell_command
• cargo test -p codex-app-server thread_read
• cargo test -p codex-app-server thread_rollback
• cargo test -p codex-app-server thread_fork
• cargo test -p codex-app-server-protocol