Reader: Enhance loading experience in post details

[kean]

The current implementation is not great because:

1. We already have everything we need to display the post we just need to wait for the web view to finish
   2. The skeleton view is a bit wacky with weird shapes and spacing

In the new version, the app displays everything it has immediately and just shows the spinner covering the web view.

https://github.com/user-attachments/assets/f791255b-edba-4f50-94bf-1a7ab1f4698c

https://github.com/user-attachments/assets/43f6d0d9-f1bc-47ab-981f-92526685ff39

To test:

Regression Notes

1. Potential unintended areas of impact

2. What I did to test those areas of impact (or what existing automated tests I relied on)

3. What automated tests I added (or what prevented me from doing so)

PR submission checklist:

• [ ] I have completed the Regression Notes.
• [ ] I have considered adding unit tests for my changes.
• [ ] I have considered adding accessibility improvements for my changes.
• [ ] I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Testing checklist:

• [ ] WordPress.com sites and self-hosted Jetpack sites.
• [ ] Portrait and landscape orientations.
• [ ] Light and dark modes.
• [ ] Fonts: Larger, smaller and bold text.
• [ ] High contrast.
• [ ] VoiceOver.
• [ ] Languages with large words or with letters/accents not frequently used in English.
• [ ] Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• [ ] iPhone and iPad.
• [ ] Multi-tasking: Split view and Slide over. (iPad)

[wpmobilebot]

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

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr23852-16dbb81
	Version	25.4.2
	Bundle ID	com.jetpack.alpha
	Commit	16dbb81a5f9ccbf19dd9c63d10ccc16f51de4e57
	App Center Build	jetpack-installable-builds #10151

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

[wpmobilebot]

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

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr23852-16dbb81
	Version	25.4.2
	Bundle ID	org.wordpress.alpha
	Commit	16dbb81a5f9ccbf19dd9c63d10ccc16f51de4e57
	App Center Build	WPiOS - One-Offs #11111

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

[dangermattic]

	1 Warning
:warning:	This PR is assigned to the milestone 25.5. The due date for this milestone has already passed. Please assign it to a milestone with a later deadline or check whether the release for this milestone has already been finished.

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