feat: add /codex:attach command for live log streaming

Adds a new `attach` subcommand to codex-companion.mjs and a matching
`/codex:attach` command definition.

**Problem:** Background Codex jobs (`/codex:rescue --background`) produce
no live output. The only way to observe progress is to poll `/codex:status`
or wait for `/codex:result` after completion — a blind black-box experience.

**Solution:** `/codex:attach [job-id]` tails the job's on-disk log file in
real time and exits cleanly when the job reaches a terminal status
(completed, failed, cancelled). If no job ID is given, it automatically
attaches to the most recent active job.

Implementation details:
- New `handleAttach()` async function in codex-companion.mjs
- Reads the job log file path from `job.logFile` (falls back to
  `resolveJobLogFile` if missing)
- Polls for new log content every 500ms (configurable via
  `--poll-interval-ms`)
- Simultaneously polls job state via `listJobs()` for terminal status
- Final log flush + closing line on exit
- No new dependencies; uses existing state/job-control infrastructure
- Does not modify any existing commands or behaviour

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 2 people

plugins/codex/commands/attach.md

@@ -0,0 +1,13 @@
+---
+description: Attach to a running Codex job and stream its live log output until it completes
+argument-hint: '[job-id] [--poll-interval-ms <ms>]'
+disable-model-invocation: true
+allowed-tools: Bash(node:*)
+---
+
+!`node "${CLAUDE_PLUGIN_ROOT}/scripts/codex-companion.mjs" attach "$ARGUMENTS"`
+
+Present the command output verbatim to the user. Do not summarize or condense it.
+
+If no active job is found, tell the user to start one with `/codex:rescue`.
+If a job ID was not specified, the command automatically attaches to the most recent active job.

plugins/codex/scripts/codex-companion.mjs

@@ -28,6 +28,7 @@ import {
   generateJobId,
   getConfig,
   listJobs,
+  resolveJobLogFile,
   setConfig,
   upsertJob,
   writeJobFile
@@ -837,6 +838,62 @@ async function handleTaskWorker(argv) {
   );
 }
 
+async function handleAttach(argv) {
+  const { options, positionals } = parseCommandInput(argv, {
+    valueOptions: ["cwd", "poll-interval-ms"],
+    booleanOptions: []
+  });
+
+  const cwd = resolveCommandCwd(options);
+  const workspaceRoot = resolveCommandWorkspace(options);
+  const pollIntervalMs = Math.max(200, Number(options["poll-interval-ms"]) || 500);
+  const reference = positionals[0] ?? "";
+
+  let job;
+  if (reference) {
+    const snapshot = buildSingleJobSnapshot(cwd, reference);
+    job = snapshot.job;
+  } else {
+    const jobs = sortJobsNewestFirst(listJobs(workspaceRoot));
+    job = jobs.find((j) => isActiveJobStatus(j.status)) ?? jobs[0] ?? null;
+  }
+
+  if (!job) {
+    process.stdout.write("No Codex job found. Start one with /codex:rescue.\n");
+    return;
+  }
+
+  const logFile = job.logFile ?? resolveJobLogFile(workspaceRoot, job.id);
+  process.stdout.write(`[attach] Job ${job.id} · status: ${job.status}\n`);
+  if (job.title) process.stdout.write(`[attach] Task: ${job.title}\n`);
+  process.stdout.write(`[attach] Log: ${logFile}\n---\n`);
+
+  let offset = 0;
+
+  function flushNewLogContent() {
+    if (!fs.existsSync(logFile)) return;
+    const content = fs.readFileSync(logFile, "utf8");
+    if (content.length > offset) {
+      process.stdout.write(content.slice(offset));
+      offset = content.length;
+    }
+  }
+
+  flushNewLogContent();
+
+  while (true) {
+    await sleep(pollIntervalMs);
+    flushNewLogContent();
+
+    const currentJob = listJobs(workspaceRoot).find((j) => j.id === job.id);
+    if (!currentJob || !isActiveJobStatus(currentJob.status)) {
+      flushNewLogContent();
+      process.stdout.write(`\n--- Job ${job.id} ${currentJob?.status ?? "gone"} ---\n`);
+      break;
+    }
+  }
+}
+
 async function handleStatus(argv) {
   const { options, positionals } = parseCommandInput(argv, {
     valueOptions: ["cwd", "timeout-ms", "poll-interval-ms"],
@@ -1015,6 +1072,9 @@ async function main() {
     case "cancel":
       await handleCancel(argv);
       break;
+    case "attach":
+      await handleAttach(argv);
+      break;
     default:
       throw new Error(`Unknown subcommand: ${subcommand}`);
   }