fix(CDPBrowser): jsdoc-parseable return type for _selectionDescriptor

Classic jsdoc cannot parse TS optional-property syntax in type
expressions; npm run def failed, breaking the Typings workflow and the
runner suite's definition test.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: DavertMik

docs/helpers/CDPBrowser.md

@@ -252,6 +252,8 @@ Builds the `{index, strict}` element-selection descriptor from the current step'
 disables strict mode for that step; otherwise `exact`/`strictMode` per-step options
 override `options.strict` to enable or cancel strict mode.
 
+Returns **([object][3] | null)** descriptor with optional `index` and `strict` keys, or `null` when neither applies.
+
 ### _textSource
 
 Resolves the text to search `see`/`dontSee`/`waitForText` against, when no explicit `context`

lib/helper/CDPBrowser.js

@@ -335,7 +335,7 @@ class CDPBrowser extends Helper {
    * disables strict mode for that step; otherwise `exact`/`strictMode` per-step options
    * override `options.strict` to enable or cancel strict mode.
    *
-   * @returns {?{index?: number, strict?: true}} `null` when neither applies.
+   * @returns {object|null} descriptor with optional `index` and `strict` keys, or `null` when neither applies.
    * @protected
    */
   _selectionDescriptor() {