Convert ReaderPost mapping to Swift

[kean]

I used TDD to reduce the risk of regression and performed manual tests.

[dangermattic]

	2 Warnings
⚠️	Modules/Package.swift was changed without updating its corresponding Package.resolved. If the change includes adding, removing, or editing a dependency please resolve the Swift packages as appropriate to your project setup (e.g. in Xcode or by running swift package resolve). If the change to the Package.swift did not modify dependencies, ignoring this warning should be safe, but we recommend double checking and running the package resolution just in case. .
⚠️	This PR is larger than 500 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

Generated by 🚫 Danger

[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	31134
	Version	PR #25301
	Bundle ID	org.wordpress.alpha
	Commit	5015185
	Installation URL	4iqjafnh1mpu8

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	31134
	Version	PR #25301
	Bundle ID	com.jetpack.alpha
	Commit	5015185
	Installation URL	5a6aj06k08oc8

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.

[sonarqubecloud]

Quality Gate passed

Issues
27 New issues
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