Support shorthand test file names (e.g. 'bugatti test ftue' → ftue.test.toml)

[codesoda]

Problem

When a user runs bugatti test ftue, they get an error because there's no file literally named ftue. They meant ftue.test.toml.

This is a common UX friction point — users naturally type the short name rather than the full filename with extensions.

Proposed solution

When the provided test file path doesn't exist as-is, try appending .test.toml before erroring:

1. User runs bugatti test ftue
2. ftue doesn't exist as a file
3. Try ftue.test.toml — if it exists, use it
4. If neither exists, show the original error

Edge cases to consider

• Path includes a directory: bugatti test tests/ftue → try tests/ftue.test.toml
• User already provides the extension: bugatti test ftue.test.toml → use as-is (current behavior)
• Ambiguity: probably not an issue since we only try one suffix