[codex] Persist Codex update prompt dedupe

[Pigbibi]

Summary

• Persist Codex CLI update prompt dedupe state by latest version.
• Reuse the existing app config directory and atomic JSON writer for codex_update_prompt_state.json.
• Add coverage for restart-style dedupe where in-memory state is empty but the version was already prompted.

Root Cause

The previous dedupe set lived only in process memory, so the same Codex CLI update prompt could be sent again after a bot restart.

Validation

• timeout 180 uv run --extra dev pytest tests/telegram_codex_bot/test_codex_update_prompt.py
• timeout 120 uv run --extra dev ruff check src/telegram_codex_bot/bot.py tests/telegram_codex_bot/test_codex_update_prompt.py

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Persist prompts only after successful notification

When Telegram returns RetryAfter (which safe_send re-raises), this save has already written the latest version to codex_update_prompt_state.json. The exception aborts notify_codex_update_available before the prompt is delivered to all users, and subsequent checks/restarts will skip the update because the version is now persisted; save the key only after the send loop completes, or roll it back on failure.

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