feat: parse retry-after from errors, cache codex usage per account

- Parse "try again at" time from rate-limit errors instead of
  fixed 1-hour cooldown, with 3-min buffer after reset
- Pass error message to rotateToken/rotateCodexToken for parsing
- Cache usage % and reset time per Codex account for dashboard
- Persist cached usage in rotation state file across restarts
- Show rate-limited Codex accounts with cached 100% + reset time
- Fix dashboard text indicators (*!/space) for monospace alignment

src/unified-dashboard.ts

@@ -616,10 +616,14 @@ async function buildUsageContent(): Promise<string> {
           });
         }
       } else {
+        // Show cached usage for rate-limited accounts
+        const pct = acct.isRateLimited && acct.cachedUsagePct != null
+          ? acct.cachedUsagePct : -1;
+        const reset = acct.resetAt || '';
         rows.push({
           name: `${label} ${acct.planType}`,
-          h5pct: -1,
-          h5reset: '',
+          h5pct: pct,
+          h5reset: reset,
           d7pct: -1,
           d7reset: '',
         });