test(gateway): fix order-dependent telegram-mock flake cluster

[mehmetkr-31]

Summary

Eight telegram gateway tests pass in isolation and in their own files but fail in a full tests/gateway run — a long-standing order-dependent flake cluster:

• test_telegram_slash_confirm.py::TestSendSlashConfirm::test_uses_markdown_v2_and_escapes_special_chars
• test_telegram_approval_buttons.py (2 tests)
• test_telegram_model_picker.py (3 tests)
• test_telegram_network_reconnect.py::test_network_error_classifier_matches_ptb_semantics (2 params)

Root cause

tests/gateway/test_dm_topics.py installed its telegram sys.modules mock unconditionally — no hasattr(sys.modules["telegram"], "__file__") real-library guard like every other telegram test — and force-reimported the adapter against it (sys.modules.pop("plugins.platforms.telegram.adapter")). Its stub also diverged from the shared one in two ways:

1. It registered a separate string-valued telegram.constants module, so ParseMode.MARKDOWN_V2 was the plain string "MarkdownV2" — its repr() is 'MarkdownV2', which fails assertions like "MARKDOWN_V2" in repr(parse_mode) that expect PTB's StrEnum repr (<ParseMode.MARKDOWN_V2>).
2. Its telegram.error was a bare MagicMock, so isinstance(exc, telegram.error.TimedOut) checks in test_telegram_network_reconnect.py broke.

Because the stub installed unconditionally and force-reimported the adapter, whichever collection order reached test_dm_topics first leaked that divergent stub into sys.modules for the rest of the session — so later telegram tests asserting real-PTB semantics failed order-dependently while passing alone.

Fix (test-only)

• test_dm_topics.py now uses the shared tests/gateway/conftest.py::_ensure_telegram_mock (guarded on the real library, comprehensive telegram.error hierarchy) instead of a divergent local stub. It was the only file that unconditionally overwrote the telegram mock.
• The shared mock now models ParseMode/ChatType as PTB-faithful StrEnum members via a small _FakeEnumMember(str): str(x) and equality return the value ("supergroup") while repr(x) shows the qualified name (<ChatType.SUPERGROUP: 'supergroup'>). That satisfies both the adapter's str(chat.type) normalization in _build_message_event and the tests' repr-based assertions, regardless of which file's mock installed first.

Verification

pytest tests/gateway -k telegram   # 1231 passed, 2 skipped (previously 8 failed in full runs)
pytest tests/gateway/test_dm_topics.py   # 40 passed

A full tests/gateway run drops from 20 order-dependent failures to only the pre-existing non-telegram flakes (test_wecom_callback, test_systemd_notify, test_channel_directory, …) that also fail on pristine main and are unrelated to this change (separate root causes, out of scope here).

🤖 Generated with Claude Code

[alt-glitch]

This was generated by AI during triage.

Duplicate of #33875: both repair the Telegram mock enum semantics causing order-dependent gateway-test failures; #33875 is the broader open fixture-cluster fix.

[teknium1]

Merged via the round-3 stability PR #74576 (commit 4673d27, your authorship preserved; the release.py hunk was rerouted to contributors/emails/ since the legacy map is frozen). Your fix landed at the poison source — PTB-faithful _FakeEnumMember in the shared conftest + removal of dm_topics' divergent local mock; the telegram cluster failures are gone (5→0). @liuhao1024 is credited in the commit as the earliest diagnoser of the class (#33875). Thanks @mehmetkr-31!