Fix ctest reporting success when requested tests match nothing (#4915)

[Omotola]

Fixes #4915

When specific tests are requested but none match a discovered test, ctest runs a filter that matches nothing and still exits 0 ("No tests were found!!!"). Callers such as the API/Copilot agent read that 0 as success, so an agent that passes a partial or non-existent test name gets told "all tests passed" when nothing ran.

This returns a failure (with a clear message) when tests exist but the requested ones weren't found. It's applied in both run paths:

• runCTestHelper (Test Explorer integration, the default) — the zero-match case was already detected and logged, now it also returns a non-zero exit code.
• runCTestDirectly (Test Explorer integration disabled) — added a guard before running ctest.

The message is also placed in the result's stderr so it can surface to the caller.

Per the issue discussion, this only fails when tests are available but the requested name isn't found — a project with no tests at all is not treated as an error.

Testing

• Reproduced the original bug: agent passing ["ClassTest"] (real tests are ClassTest.Test1/2/3) reported success with nothing run.
• Confirmed ctest -R <nonMatching> exits 0, while the extension now returns a failure for that case.
• yarn compile clean; unit tests pass (only the pre-existing select-debugger fakebin failures remain, unrelated).

Before

After