Fix error for running build when there is multiple admin links and ui extensions

[vividviolet]

WHY are these changes introduced?

When wrapper helpers forward optional fields as explicit undefined, those undefined values were shadowing the computed defaults in createExtensionSpecification. This meant fields like experience, uidStrategy, and buildConfig could end up as undefined instead of their intended default values.

WHAT is this pull request doing?

Before merging the caller-supplied spec object into the defaults, explicit undefined values are stripped from spec using pickBy. This ensures that defaults are preserved when optional fields are forwarded as undefined by wrapper helpers, rather than being overwritten.

A regression test is added to verify that explicitly passing undefined for experience, uidStrategy, buildConfig, and clientSteps still results in the correct defaults being applied.

How to test your changes?

Run the integration tests for the extension specification:

pnpm test packages/app/src/cli/models/extensions/specification.integration.test.ts

The new test case does not let explicit-undefined spec keys shadow the computed defaults should pass.

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add

[vividviolet]

• Fix error for running build when there is multiple admin links and ui extensions #7347 👈 (View in Graphite)
• main

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