Backport descriptive MTP exit-code summaries to .NET 10 and .NET 11

### Describe the bug

`dotnet test` in Microsoft.Testing.Platform mode reports a non-successful test application with only the numeric exit code and documentation link:

```text
Test run summary: Zero tests ran
error: 1

total: 0
failed: 0
succeeded: 0
skipped: 0

Test run completed with non-success exit code: 5 (see: https://aka.ms/testingplatform/exitcodes)
```

Microsoft.Testing.Platform 2.4 added concise descriptions for known exit codes in microsoft/testfx#10882. For exit code 5, the intended final line is:

```text
Test run completed with non-success exit code: 5. The command-line arguments are invalid. See: https://aka.ms/testingplatform/exitcodes
```

However, `dotnet test` compiles a vendored copy of the terminal reporter, so updating the Microsoft.Testing.Platform package does not update this SDK-owned output.

### Expected behavior

Synchronize the descriptive exit-code reporting from microsoft/testfx#10882 into the SDK reporter. Keeping `Test run summary: Zero tests ran` is acceptable, provided it is followed by the actionable exit-code description.

Please service this behavior into both the .NET 10 and .NET 11 SDK release branches, with coverage for invalid command-line exit code 5 in run and discovery summaries.

### Related work

- microsoft/testfx#10868
- microsoft/testfx#10882
- dotnet/sdk#55939 handles the separate .NET 10 pre-handshake diagnostics and `--nologo` compatibility work, but does not add the descriptive final exit-code line.

Start at the vendored terminal reporter used by the dotnet test entry point and compare its exit-code reporting with microsoft/testfx#10882. Add coverage for invalid command-line exit code 5 in both run and discovery summaries, then verify the descriptive final line is synchronized into the .NET 10 and .NET 11 SDK release branches.

Written by the indexing model from the issue text.