What kind of change does this PR introduce?

Bug fix

What is the current behavior?

When source.addMissingImports code action is triggered, it calls ensureConfigurationForDocument to send the user's preferences to the TypeScript server. However, this method calls getFormattingOptions(document) which looks for a visible text editor matching the document. If no visible editor is found (which can happen when the code action is triggered via keybinding or command palette), the method returns undefined and ensureConfigurationForDocument returns early without sending any configuration to the TS server.

This means user preferences like preferTypeOnlyAutoImports are never communicated to the TypeScript server, causing it to use its default behavior instead. Users report that source.addMissingImports always adds type keyword to imports regardless of their preferTypeOnlyAutoImports: false setting, while the quick fix lightbulb (which goes through a different code path) works correctly.

Closes #272479

What is the new behavior?

When no visible editor is found for the document, the method now falls back to { tabSize: undefined, insertSpaces: undefined } instead of returning early. This means the formatting options will be unset (letting the TS server use its own defaults for tab size and spaces), but critically, all user preferences (including preferTypeOnlyAutoImports, quotePreference, importModuleSpecifierPreference, etc.) will still be sent to the TS server.

Additional context

The fix is minimal: replace the conditional guard with a nullish coalescing fallback:

// Before
const formattingOptions = this.getFormattingOptions(document);
if (formattingOptions) {
    return this.ensureConfigurationOptions(document, formattingOptions, token);
}

// After
const formattingOptions = this.getFormattingOptions(document)
    ?? { tabSize: undefined, insertSpaces: undefined };
return this.ensureConfigurationOptions(document, formattingOptions, token);

The tabSize: undefined and insertSpaces: undefined values are already valid for the FormattingOptions interface and the TS server's configure command handles them gracefully by using its own defaults.