fix: Matrix !relogin UnboundLocalError

[WODE25500]

What

!relogin crashed with UnboundLocalError for any configured Matrix bridge.

logout_cmd was assigned on a line after an unconditional continue inside the if not bridge.login_command or not bridge.dm_room_id branch. Because the continue always fired on that path, logout_cmd was never assigned, and the following lines.append(...) ran for the configured path, so any bridge with both login_command and dm_room_id raised UnboundLocalError and the admin command always crashed.

The fix moves the assignment above the if.

Tests

Added tests/unit_tests/test_matrix_relogin.py with four self-contained regression tests (no SDK / langbot_plugin dependency). All pass locally.

Notes

• Rebased onto the latest master.
• The Coze stream tail flush and Langflow tweaks default fixes from the earlier revision were split into separate PRs per review feedback.

[github-actions]

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[WODE25500]

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[dadachann]

Thanks for the fixes, @WODE25500. The recovery-key/password-reset hardening has already been addressed in #2477, which is merged into master, so please drop the duplicate recovery-key changes.

Please rebase onto the latest master and keep this PR focused only on the Matrix !relogin fix and its regression test. Move the unrelated Coze and Langflow changes (including the Coze test) to separate PRs, and update the title and description accordingly.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/langbot/pkg/platform/sources/matrix.py	0.00%	1 Missing ⚠️

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[WODE25500]

@dadachann Done: rebased onto the latest master, dropped the duplicate recovery-key changes (already covered by #2477), and split the unrelated fixes into separate PRs:

• Coze stream tail flush: fix: flush Coze stream tail when no done event is emitted #2518
• Langflow tweaks default: fix: default Langflow tweaks to empty object when unset #2519

This PR now contains only the Matrix !relogin fix and its regression test.