Move message history out of core (#21278)

## Why

Message history was implemented inside `codex-core` and surfaced through
core protocol ops and `SessionConfiguredEvent` fields even though the
current consumer is TUI-local prompt recall. That made core own UI
history persistence and exposed `history_log_id` / `history_entry_count`
through surfaces that app-server and other clients do not need.

This change moves message history persistence out of core and keeps the
recall plumbing local to the TUI.

## What changed

- Added a new `codex-message-history` crate for appending, looking up,
trimming, and reading metadata from `history.jsonl`.
- Removed core protocol history ops/events: `AddToHistory`,
`GetHistoryEntryRequest`, and `GetHistoryEntryResponse`.
- Removed `history_log_id` and `history_entry_count` from
`SessionConfiguredEvent` and updated exec/MCP/test fixtures accordingly.
- Updated the TUI to dispatch local app events for message-history
append/lookup and keep its persistent-history metadata in TUI session
state.

## Validation

- `cargo test -p codex-message-history -p codex-protocol`
- `cargo test -p codex-exec event_processor_with_json_output`
- `cargo test -p codex-mcp-server outgoing_message`
- `cargo test -p codex-tui`
- `just fix -p codex-message-history -p codex-protocol -p codex-core -p
codex-tui -p codex-exec -p codex-mcp-server`

codex-rs/mcp-server/src/codex_tool_runner.rs

@@ -347,7 +347,6 @@ async fn run_codex_tool_session_inner(
                     | EventMsg::TurnDiff(_)
                     | EventMsg::WebSearchBegin(_)
                     | EventMsg::WebSearchEnd(_)
-                    | EventMsg::GetHistoryEntryResponse(_)
                     | EventMsg::PlanUpdate(_)
                     | EventMsg::TurnAborted(_)
                     | EventMsg::UserMessage(_)

codex-rs/mcp-server/src/outgoing_message.rs

@@ -310,8 +310,6 @@ mod tests {
                 active_permission_profile: None,
                 cwd: test_path_buf("/home/user/project").abs(),
                 reasoning_effort: Some(ReasoningEffort::default()),
-                history_log_id: 1,
-                history_entry_count: 1000,
                 initial_messages: None,
                 network_proxy: None,
                 rollout_path: Some(rollout_file.path().to_path_buf()),
@@ -357,8 +355,6 @@ mod tests {
             active_permission_profile: None,
             cwd: test_path_buf("/home/user/project").abs(),
             reasoning_effort: Some(ReasoningEffort::default()),
-            history_log_id: 1,
-            history_entry_count: 1000,
             initial_messages: None,
             network_proxy: None,
             rollout_path: Some(rollout_file.path().to_path_buf()),
@@ -397,8 +393,6 @@ mod tests {
                 "permission_profile": session_configured_event.permission_profile,
                 "cwd": test_path_buf("/home/user/project"),
                 "reasoning_effort": session_configured_event.reasoning_effort,
-                "history_log_id": session_configured_event.history_log_id,
-                "history_entry_count": session_configured_event.history_entry_count,
                 "rollout_path": rollout_file.path().to_path_buf(),
             }
         });
@@ -428,8 +422,6 @@ mod tests {
             active_permission_profile: None,
             cwd: test_path_buf("/home/user/project").abs(),
             reasoning_effort: Some(ReasoningEffort::default()),
-            history_log_id: 1,
-            history_entry_count: 1000,
             initial_messages: None,
             network_proxy: None,
             rollout_path: Some(rollout_file.path().to_path_buf()),
@@ -469,8 +461,6 @@ mod tests {
                 "permission_profile": session_configured_event.permission_profile,
                 "cwd": test_path_buf("/home/user/project"),
                 "reasoning_effort": session_configured_event.reasoning_effort,
-                "history_log_id": session_configured_event.history_log_id,
-                "history_entry_count": session_configured_event.history_entry_count,
                 "rollout_path": rollout_file.path().to_path_buf(),
             }
         });