More tests, cleanup for direct connect form

[noeldevelops]

Summary of Changes

• Backfills unit tests for mergeSecrets
• Updates some checks so that we don't have to @ts-expect-error all over the place as much
• Adds basic functional (Playwright) tests to confirm form renders, submits in happy case

Any additional details or context that should be provided?

• Still a few @ts-expect-error comments in the form ts - it's proving hard to check these types include or are instances of the credential objects in this file where they are are actually inertial Signals under the hood.

Pull request checklist

Please check if your PR fulfills the following (if applicable):

Tests

• Added new
• Updated existing
• Deleted existing

Other

• All new disposables (event listeners, views, channels, etc.) collected as for eventual cleanup?

• Does anything in this PR need to be mentioned in the user-facing CHANGELOG or README?
• Have you validated this change locally by packaging and installing the extension .vsix file?

  gulp clicktest

[shouples]

LGTM, just one question about collapsing some of the nested if statements but not a blocker