fix(codex): parse the new rollout schema (item_completed) from Codex ≥ ~0.149

[DaeYounLee]

Problem

Recent Codex CLI versions (observed on v0.149) changed the rollout session format. Sessions recorded by these versions show up in abtop with:

• empty chat, no tool timeline, no turn count
• status stuck on Waiting even while the model is actively working
• initial_prompt never populated, so the session summary stays —

Root cause

The codex collector matches the old event vocabulary (event_msg → user_message / agent_message / task_complete, response_item → function_call). New rollouts no longer emit any of those — everything arrives as event_msg with payload.type == "item_completed", wrapping a typed item:

{"type":"event_msg","payload":{"type":"item_completed","item":{
  "type":"AgentMessage","content":[{"type":"Text","text":"…"}],"phase":"final_answer"},
  "started_at_ms":1787291153283,"completed_at_ms":1787291154027}}

{"type":"event_msg","payload":{"type":"item_completed","item":{
  "type":"CommandExecution","command":["/bin/zsh","-lc","sed -n '1,240p' README.md"],
  "parsed_cmd":[{"type":"read","cmd":"sed -n '1,240p' README.md","path":"/work/README.md"}],
  "started_at_ms":1787291167583,"completed_at_ms":1787291168442}}

{"type":"event_msg","payload":{"type":"item_completed","item":{
  "type":"FileChange","changes":{"/work/report.md":{"type":"add"}}}}}

(Synthetic samples; field shapes match real rollouts. Note the inconsistent casing — "Text" on AgentMessage content vs "text" on UserMessage.)

Changes

One new arm in the event_msg match plus a handle_item_completed() helper:

item type	handled as
UserMessage	chat (User role), initial_prompt, marks model generating
AgentMessage	chat (Assistant role), turn count, clears generating state
CommandExecution	tool call — name from parsed_cmd[0].type (read/write/…), real duration from started_at_ms/completed_at_ms; file accesses from parsed_cmd[].path
FileChange	file accesses (add → Write, else Edit) plus an edit tool-call entry
Extension	tool call named by kind (e.g. web.search) with its query

Two small state fixes for the new schema: task_started now marks the model as generating (there is no user_message event anymore to do it), and turn_aborted clears it.

Side effect worth calling out: codex sessions gain file_accesses — the old schema never carried file information, so AgentSession.file_accesses was always empty for codex. FileChange and parsed_cmd now populate it, capped at MAX_FILE_ACCESSES like the claude collector.

Existing text hygiene is reused: chat goes through clean_chat_text, tool args through sanitize_tool_arg, MAX_CHAT_MESSAGES still applies.

Relation to #160 / #161

Complementary, not overlapping: #161 targets the previous generation (Codex 0.144.x — custom_tool_call in response_item, intermediate agent_message events), while this PR targets the item_completed vocabulary that replaced it. One coordination note: 0.149 rollouts still write custom_tool_call alongside item_completed.CommandExecution for the same call — this PR reads only the latter, so nothing double-counts today, but if both PRs land it would be worth deduplicating by call_id in a follow-up.

Backward compatibility

The old-schema arms are untouched and the two vocabularies never coexist in one file, so rollouts from older Codex versions parse exactly as before. All existing tests pass unchanged.

Testing

• 4 new unit tests: chat from both content casings + turn counting, trailing-UserMessage generating state, CommandExecution tool call with real duration + file access from parsed_cmd, FileChange → Write/Edit accesses
• cargo test — 204 passed, 0 failed; cargo clippy --all-targets -- -D warnings clean
• Verified against live Codex 0.149 sessions: a session that previously showed 0 chat / 0 tools / 0 files and a stuck Waiting status now reports 21 chat messages, 18 tool calls, 13 file accesses, 11 turns, correct status