config: add auto-compact settings for Claude and Codex agents

Claude: CLAUDE_AUTOCOMPACT_PCT_OVERRIDE=50 (~500K on 1M context)
Codex: model_auto_compact_token_limit=258000 (matching CLI default)

src/token-rotation-base.ts

@@ -0,0 +1,71 @@
+/**
+ * Token Rotation Base Utilities (SSOT)
+ *
+ * Shared algorithms for Claude and Codex token rotation.
+ * Extracted from token-rotation.ts and codex-token-rotation.ts
+ * to eliminate duplicate implementations.
+ */
+
+export const BUFFER_MS = 3 * 60_000; // 3 min buffer after reset time
+export const DEFAULT_COOLDOWN_MS = 3_600_000; // 1 hour fallback
+
+/**
+ * Parse "try again at Mar 26th, 2026 9:00 AM" or "resets at ..." from
+ * an error message. Returns timestamp in ms, or null if not found.
+ *
+ * Uses the wider regex from token-rotation.ts that also matches
+ * "resets at" patterns (codex-token-rotation only matched "try again at").
+ */
+export function parseRetryAfterFromError(error?: string): number | null {
+  if (!error) return null;
+  const match = error.match(
+    /(?:try again at|resets?\s+(?:at\s+)?)\s*(\w+ \d{1,2}(?:st|nd|rd|th)?,?\s+\d{4}\s+\d{1,2}:\d{2}\s*(?:AM|PM)?)/i,
+  );
+  if (!match) return null;
+  try {
+    const cleaned = match[1].replace(/(\d+)(?:st|nd|rd|th)/i, '$1');
+    const ts = new Date(cleaned).getTime();
+    if (Number.isNaN(ts)) return null;
+    return ts;
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Compute when a rate-limited token should become available again.
+ * Parses retry-after from error message, falling back to DEFAULT_COOLDOWN_MS.
+ */
+export function computeCooldownUntil(error?: string): number {
+  const retryAt = parseRetryAfterFromError(error);
+  if (retryAt) return retryAt + BUFFER_MS;
+  return Date.now() + DEFAULT_COOLDOWN_MS;
+}
+
+/**
+ * Find the next available (non-rate-limited) item in a rotation pool.
+ * Returns the index, or null if all are exhausted.
+ *
+ * This is the shared rotation algorithm used by both Claude token rotation
+ * and Codex account rotation.
+ */
+export function findNextAvailable<
+  T extends { rateLimitedUntil: number | null },
+>(
+  items: T[],
+  currentIndex: number,
+  opts?: { ignoreRateLimits?: boolean },
+): number | null {
+  const now = Date.now();
+  const ignoreRL = opts?.ignoreRateLimits ?? false;
+
+  for (let i = 1; i < items.length; i++) {
+    const idx = (currentIndex + i) % items.length;
+    const item = items[idx];
+    if (ignoreRL || !item.rateLimitedUntil || item.rateLimitedUntil <= now) {
+      return idx;
+    }
+  }
+
+  return null;
+}