The OAuth profile removal dropped cross-user permission tests (deck, files,
notes) that validated Nextcloud sharing/ACL enforcement through MCP tools.
These tested general functionality, not OAuth-specific behavior.
Restores coverage with login-flow fixtures and 9 tests covering file share
read/write enforcement, folder sharing, Deck board ACL view/edit, and
per-user resource isolation for files, boards, and notes.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>