Harden TDLib large-media download path and address review follow-ups

[speech115]

Summary

Closes all 7 ultrareview findings on the TDLib large-media download path.

First commit (5b3405b) addressed:

• Document Codex-assisted maintainer workflows #3 Security: DB encryption key configurable via TELEGRAM_TDLIB_DB_ENCRYPTION_KEY instead of a hardcoded constant.
• Add a short demo video or GIF for Default Mode #2 Correctness: try_acquire_with_timeout is now async (asyncio.sleep) so lock polling no longer blocks the event loop shared with the live Telethon client.
• Harden Telegram MCP plugin runtime #1 Performance: copy the downloaded file to dest then deleteFile the TDLib-side copy (best-effort) so files_directory doesn't grow unbounded.
• Add plugin cache validation guide #6 Performance: messageAnimation supported in extract_file_id_from_message so large GIFs routed as video/* don't dead-end into a wasted start + fallback.
• Add Codex Security threat-model review workflow #5 Correctness: tolerate a malformed TELEGRAM_TDLIB_DOWNLOAD_THRESHOLD_MB instead of failing the whole download.
• Plus a hang fix: start_client_ready bounds the readiness wait so a revoked/absent session falls back instead of blocking forever.

Second commit (7faf6b7) closes the remaining two:

• Improve installation guide for a clean local setup #4 Correctness: the TDLib path re-resolves the raw t.me URL via getMessageLinkInfo, which for ?comment=/thread links can land on a different message than the Telethon path (which resolves by parsed chat/message_id). New assert_expected_size() compares the downloaded byte count to the size Telethon saw and raises TdlibDownloadError on mismatch, so the caller safely falls back to the correctly-resolved Telethon download instead of silently saving the wrong file.
• docs: clarify first-run install steps #7 Maintainability: large TDLib downloads used synchronous=True and stayed silent for minutes. When not quiet, downloads now run asynchronously and poll getFile, feeding the same _make_progress callback the Telethon path already uses. quiet mode still downloads synchronously and silently.

Verification

PYTHONPATH=src .venv/bin/python -m unittest tests.test_tdlib_download tests.test_download_post

Ran 44 tests in 0.308s
OK

Full mcp/tests suite (unittest discover -s tests -p 'test_*.py'):

• clean HEAD (before second commit): Ran 412 tests — failures=1, errors=9
• this branch: Ran 416 tests — failures=1, errors=9

The 1 failure + 9 errors are pre-existing, in test_runtime.py (pydantic Settings requires api_id/api_hash, absent from this worktree's env; reproduces on clean HEAD). No new failures; the 4 added tests (AssertExpectedSizeTests, DownloadWithProgressTests) pass. compileall and git diff --check (whitespace) clean.

🤖 Generated with Claude Code

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Останавливайте TDLib-клиент при таймауте готовности

Если TDLib-сессия не авторизована или отозвана, start_client_ready() теперь поднимает TdlibDownloadError после таймаута, но этот вызов находится до try/finally, который делает await client.stop(). В этом сценарии уже запущенный pytdbot.Client не останавливается перед fallback на Telethon, поэтому повторные большие скачивания со stale-сессией могут оставлять фоновые TDLib-клиенты/открытую базу, хотя документация обещает только ограниченную задержку; оберните старт и последующую работу одним try/finally после создания клиента.

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