* Fix Rule 1b violation in PowerQuery List() outer catch block

- Remove catch block creating fake 'Error Query' entries
- Replace with continue statement to skip problematic queries
- Prevents exception suppression (Rule 1b compliance)
- Allows fault-tolerant listing: one bad query doesn't break entire list
- All 16 PowerQuery tests pass

* Remove inefficient try-catch in PowerQuery Refresh()

- Remove inner try-catch that suppressed COMException
- Let exceptions propagate naturally (Rule 1b)
- Remove complex fallback logic checking Success flag
- Simpler, more efficient: just throw on error
- All 16 PowerQuery tests pass

* Enforce sequential test execution and remove obsolete test

- Add xunit.runner.json to all test projects (Core, CLI, McpServer)
- Configure parallelizeAssembly: false, maxParallelThreads: 1
- Remove obsolete VbaCommandsTests.Trust.TrustScope.cs (skipped test)
- Ensures stable test execution for Excel COM interop