fix(telegram): route PTB NetworkError to reconnect ladder in polling heartbeat

[liuhao1024]

What does this PR do?

The persistent Telegram polling heartbeat (_polling_heartbeat_loop) did not recognize python-telegram-bot (PTB) NetworkError or TimedOut exceptions as connectivity failures. These PTB exceptions inherit from TelegramError, not OSError, so the existing handler (asyncio.TimeoutError, OSError) missed them. A broad except Exception block subsequently swallowed these errors silently, preventing the gateway from detecting and recovering dead TCP connections.

This fix extracts the reconnect trigger logic into a helper and explicitly checks for PTB NetworkError / TimedOut in the exception handler, routing them to the existing reconnect ladder. Non-connectivity PTB errors (e.g., BadRequest, InvalidToken) remain swallowed as before.

Related Issue

Fixes #62047

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• plugins/platforms/telegram/adapter.py: Modified _polling_heartbeat_loop to catch and handle telegram.error.NetworkError and telegram.error.TimedOut as connectivity failures. Added a local helper _trigger_reconnect to deduplicate the reconnect scheduling logic.
• tests/gateway/test_telegram_network_reconnect.py: Added regression tests for PTB NetworkError, TimedOut (trigger reconnect) and BadRequest (ignore).

How to Test

1. Run the new regression tests: pytest tests/gateway/test_telegram_network_reconnect.py::test_heartbeat_loop_triggers_reconnect_on_ptb_network_error tests/gateway/test_telegram_network_reconnect.py::test_heartbeat_loop_triggers_reconnect_on_ptb_timed_out tests/gateway/test_telegram_network_reconnect.py::test_heartbeat_loop_ignores_ptb_bad_request
2. Run the full Telegram network reconnect test suite to ensure existing behavior is preserved: pytest tests/gateway/test_telegram_network_reconnect.py
3. Observed result: All 3 new tests pass, confirming that PTB NetworkError and TimedOut now trigger _handle_polling_network_error (task created), while BadRequest does not. Existing tests for OSError and asyncio.TimeoutError continue to pass.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass (ran subset for gateway/telegram).
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS (via local pytest run).

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A (added comments in code)
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A (platform-agnostic exception handling)
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A