fix(document): avoid setting _skipMarkModified when setting nested path with merge option

[vkarpov15]

Fix #11913

Summary

Looks like this _skipMarkModified option isn't necessary - it was intended to prevent marking subpaths as modified before when we added the merge option. It was introduced here: 98150ac

Examples

[Copilot]

Pull Request Overview

This PR fixes issue #11913 by removing the unnecessary _skipMarkModified flag when setting nested paths with the merge option. The changes include a new test case to verify that only the intended subpaths are marked modified and an update in the document set logic to remove the _skipMarkModified option.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
test/document.test.js	Adds a test case to validate proper modified path behavior.
lib/document.js	Removes the _skipMarkModified flag in nested path setting.

Comments suppressed due to low confidence (2)

test/document.test.js:14450

• [nitpick] Consider adding a short inline comment in the test to clarify why the modifiedPaths are expected to include both the parent ('name') and the nested ('name.first') keys, which will help future maintainers understand the expected behavior for the merge option.

    human.set(h, null, null, { merge: true });

lib/document.js:1117

• The removal of the _skipMarkModified flag is intentional per the issue, but ensure that this change doesn't lead to unintended marking of unchanged subpaths. It would be beneficial to double-check that the merge option behavior remains consistent in all nested update scenarios.

        this.$set(pathName, valForKey, constructing, options);