Better error message when running sources without a sources directory

[zachstence]

Description

Resolves #2496

Checklist

• For UI or styling changes, I have added a screenshot or gif showing before & after
• I have added a changeset
  - I have added to the docs where applicable
  - I have added to the VS Code extension where applicable

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[changeset-bot]

🦋 Changeset detected

Latest commit: 9efe214

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 8 packages

Name	Type
@evidence-dev/sdk	Patch
my-evidence-project	Patch
@evidence-dev/evidence	Patch
@evidence-dev/component-utilities	Patch
@evidence-dev/core-components	Patch
@evidence-dev/components	Patch
evidence-test-environment	Patch
e2e-spa	Patch

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