`test_the_member_hint_appears_only_for_a_member` fails when the checkout path contains "superstudy"

`tests/test_campaign.py::test_the_member_hint_appears_only_for_a_member` asserts `"superstudy" not in str(e.value)`, but the refusal message embeds the running venv's absolute path. Any checkout whose path contains the word fails spuriously (`.worktrees/status-superstudy` did; dodged by renaming the branch).

Fix: assert on the hint sentence (`update-env --study`) instead of the bare word, and check the other `not in str(e.value)` assertions for the same shape: a negative assertion against a word that can appear in an unrelated part of the message (a path, a label, a dataset id).

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Start in tests/test_campaign.py at test_the_member_hint_appears_only_for_a_member and run that test to reproduce the path-dependent failure. Replace the bare-word negative check with an assertion about the update-env --study hint sentence, then inspect nearby str(e.value) negative assertions for the same false-positive shape. Done means the tests pass even when the checkout path contains superstudy and unrelated words are not used as exclusion evidence.

Written by the indexing model from the issue text.