0.4.12 — align test assertions with error-message wording

Aligns stale unit-test assertions ('All 7 IDs' / 'Try search_datasets') with current transport-agnostic error wording ('All 10 IDs' / 'Search by keyword or enumerate'). Added regex guard test mirroring rba-mcp's no-MCP-tool-refs check. 324 unit tests pass.