docs: reference vitest-base config

[itsdevdom]

PR Checklist

Please check to confirm your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular-cli/blob/main/CONTRIBUTING.md#-commit-message-guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

Current documentation mistakenly still references vitest.config.ts as an example to apply Vite config customizations.

What is the new behavior?

Documentation now references the correct vitest-base.config.ts as an example to apply Vite config customizations, both in the unit test schema and the Karma-to-Vite migration message.

Does this PR introduce a breaking change?

• Yes
• No

Other information

• Original change: fix(@angular/build): introduce vitest-base.config for test configuration #31621

[gemini-code-assist]

Code Review

This pull request updates the default Vitest configuration filename from vitest.config.ts to vitest-base.config.ts within the unit-test builder schema and the Karma-to-Vitest migration schematic. Feedback was provided to improve the migration warning message by explicitly mentioning the need to enable the runnerConfig option and refining the formatting of the file reference.

[alan-agius4]

Can you also please update the commit type to docs

[itsdevdom]

Commit type and PR title are now docs.

[alan-agius4]

LGTM, thanks for your contribution.

[alan-agius4]

This PR was merged into the repository. The changes were merged into the following branches:

• main: 599274e

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