Codex switch: translate settings-index ↔ rotation-index by auth path (#51)

settings-store lists codex accounts as
  index 0 = ~/.codex/auth.json (default)
  index N = ~/.codex-accounts/{N}/auth.json
but codex-token-rotation only loads ~/.codex-accounts/{N} when those
dirs exist (it ignores ~/.codex/auth.json in that mode), so the
rotation array's indices are off-by-one vs settings indices.

Old buggy behavior:
- "사용중" badge pointed at the wrong account.
- Clicking 전환 on UI #N called setCurrentCodexAccountIndex(N) which
  selected rotation array element N — typically a different
  ~/.codex-accounts/{N+1} entry. Effectively the UI told us a
  different account was now active than what the next codex spawn
  actually used.

Fix
- New findCodexAccountIndexByAuthPath(path) on the rotation module
  exposes a path-based lookup.
- New getActiveCodexSettingsIndex() / setActiveCodexSettingsIndex(idx)
  in settings-store translate via codexAuthPath() ↔
  findCodexAccountIndexByAuthPath().
- /api/settings/accounts.codexCurrentIndex and PUT
  /api/settings/accounts/codex/current both go through the
  settings-side translation, so UI indices are now authoritative.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

src/settings-store.ts

@@ -15,6 +15,12 @@ import fs from 'node:fs';
 import os from 'node:os';
 import path from 'node:path';
 
+import {
+  findCodexAccountIndexByAuthPath,
+  getActiveCodexAuthPath,
+  setCurrentCodexAccountIndex as setRotationIndex,
+} from './codex-token-rotation.js';
+
 export interface ClaudeAccountSummary {
   index: number;
   expiresAt: number | null;
@@ -441,6 +447,54 @@ export async function refreshCodexAccount(
   return summary;
 }
 
+/**
+ * settings-store lists codex accounts in an order that includes the default
+ * `~/.codex/auth.json` as index 0 plus `~/.codex-accounts/{N}` as index N.
+ * The rotation array (codex-token-rotation) only loads `~/.codex-accounts/{N}`
+ * when those dirs exist (it ignores `~/.codex/auth.json` in that mode), so its
+ * array indices are off-by-one vs. the settings indices. Translate via path.
+ */
+export function getActiveCodexSettingsIndex(): number | null {
+  const activePath = getActiveCodexAuthPath();
+  if (!activePath) return null;
+  // Walk the same listing order as listCodexAccounts() to find the matching
+  // settings-store index.
+  if (codexAuthPath(0) === activePath && fs.existsSync(activePath)) {
+    return 0;
+  }
+  const dir = path.join(os.homedir(), '.codex-accounts');
+  if (fs.existsSync(dir)) {
+    const indices = fs
+      .readdirSync(dir)
+      .filter((e) => /^\d+$/.test(e))
+      .map((e) => Number.parseInt(e, 10))
+      .filter((n) => Number.isFinite(n) && n >= 1)
+      .sort((a, b) => a - b);
+    for (const i of indices) {
+      if (codexAuthPath(i) === activePath) return i;
+    }
+  }
+  return null;
+}
+
+export function setActiveCodexSettingsIndex(settingsIndex: number): void {
+  const file = codexAuthPath(settingsIndex);
+  if (!fs.existsSync(file)) {
+    throw new Error(
+      `codex auth.json not found for settings index ${settingsIndex}`,
+    );
+  }
+  const rotationIndex = findCodexAccountIndexByAuthPath(file);
+  if (rotationIndex === null) {
+    throw new Error(
+      `codex switch: settings #${settingsIndex} (${file}) is not part of the rotation pool. ` +
+        `Rotation only manages accounts under ~/.codex-accounts/. ` +
+        `If you want to use ~/.codex/auth.json directly, remove the ~/.codex-accounts dir first.`,
+    );
+  }
+  setRotationIndex(rotationIndex);
+}
+
 export async function refreshAllCodexAccounts(): Promise<{
   refreshed: number[];
   failed: Array<{ index: number; error: string }>;