refactor(codex-manager): extract login machinery (phase 4)

Audit roadmap §4.1.1 phase 4: move the interactive login control loop and
the OAuth/device sign-in machinery out of lib/codex-manager.ts into focused
modules under lib/codex-manager/, with zero behavior change. Bodies are
verbatim; the only mechanical edits are closure variable -> state field and
closure capture -> deps parameter.

Module map (new files):
- lib/codex-manager/login-oauth.ts (491 lines): runOAuthFlow, runSignInFlow,
  promptManualCallback, resolveAccountSelection, persistAccountPool,
  syncSelectionToCodex, isOAuthCancellation/isAbortError, token/mode types.
- lib/codex-manager/login-menu-actions.ts (413 lines): sign-in mode and
  backup-restore prompts plus handleManageAction and its
  selection-index/storage-matching helpers.
- lib/codex-manager/login-action-panel.ts (272 lines): runActionPanel and
  the waitForMenuReturn return-to-menu prompt.
- lib/codex-manager/login-flow.ts (566 lines): runAuthLogin entry point,
  runAuthLoginFlow outer loop (onboarding/add-account, restore-backup), and
  runLoginDashboardLoop. The previously closure-mutable menu quota-refresh
  variables (pendingMenuQuotaRefresh, menuQuotaRefreshStatus,
  skipNextMenuQuotaAutoRefresh, menuQuotaRefreshGeneration) are now an
  explicit MenuQuotaRefreshState object created in runAuthLoginFlow and
  passed through; the loginFlow label-based control flow is preserved, with
  the extracted dashboard loop signalling "add-account" | "exit" where it
  previously used break/return.

runForecast and createRepairCommandDeps stay in lib/codex-manager.ts (both
are also used by the CLI command registry) and are handed to the login flow
via a LoginFlowDeps object, so no extracted module imports codex-manager.ts
back. The public facade of lib/codex-manager.ts is unchanged
(formatBackupSavedAt, styleAccountDetailText, autoSyncActiveAccountToCodex,
runCodexMultiAuthCli).

lib/codex-manager.ts: 2,266 -> 690 lines.

https://claude.ai/code/session_01XNtnkLbBiXZxfQQYLMpucB

Author: claude