feat: add AGT V2 retry continuation and interactive gates

[ZHOUKAILIAN]

Summary

• Add codex_exec executor selection and JSONL failure classification so turn.failed / stream errors become traceable runtime failures with retry metadata.
• Add retryable stage auto-retry for Product/Dev/QA runs, plus agt2 retry to continue the same blocked session after a human resolves the blocker.
• Add same-terminal interactive prompts for agt2 deliver/run waiting and blocked states, so approval/retry can continue without opening a second terminal.

Test Plan

• npm run typecheck
• npm run build:packages
• npm test
• AGT_EXECUTOR=local_fallback node packages/cli/dist/V2/index.js deliver --repo-root "$TMP" --state-root "$TMP/.agt2" --no-task-worktree --interactive "interactive smoke" then q at the waiting gate