Reader: Add support for <br> tags in excerpt generator

[kean]

Fixes CMM-82: Reader incorrectly renders newlines in excerpts.

Prerequisite: #25400.

This PR is for excerpts generated on the client. In the case of the post from the issue, the lack of whitespaces is backed in on the server. I opened a separate issue for the Loop team. The client-side one should be considered fixed, which you can see in the unit tests.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Configuration	Release-Alpha
	Build Number	31623
	Version	PR #25392
	Bundle ID	org.wordpress.alpha
	Commit	0e16c02
	Installation URL	3qgfudhl8hm80

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Configuration	Release-Alpha
	Build Number	31623
	Version	PR #25392
	Bundle ID	com.jetpack.alpha
	Commit	0e16c02
	Installation URL	55qof6uvffjeo

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[wpmobilebot]

🤖 Build Failure Analysis

This build has failures. Claude has analyzed them - check the build annotations for details.

[kean]

In order to use WordPressShared in WordPressKitModel, it looks like I first need to resolve some issues with ObjC headers and helper methods duplicated in WPKit:

Found the issue. Both WordPressSharedObjC and WordPressKitObjC have a public header named WPMapFilterReduce.h. Now that WordPressKitObjC transitively depends on WordPressSharedObjC (via WordPressKitModels → WordPressShared → WordPressSharedObjC), the compiler resolves #import "WPMapFilterReduce.h" to WordPressSharedObjC's version — which defines WPMapBlock/WPFilterBlock but not WPKitMapBlock/WPKitFilterBlock.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[crazytonyli]

FYI, the unit tests job failed.

[wpmobilebot]

Version 26.8 has now entered code-freeze, so the milestone of this PR has been updated to 26.9.