chore(playground): load the latest published Ionic in demos for unreleased majors - #4829

Issue URL: internal

What is the current behavior?

The playground generator writes @ionic/core@<version> into each demo.html for the version you pick. For a major not yet on npm, such as 10 on major-10.0, jsDelivr returns 404 and the demo renders blank. Every v10 playground so far has been fixed by hand, 884 CDN references on major-10.0 alone.

What is the new behavior?

• The generator reads the latest dist-tag from npm. If the picked major is newer, demo.html loads the latest published major and gets a TODO(FW-XXXX) comment above the CDN links.
• The generator prints a note saying the demo renders but APIs new in that major will not work until it is published, and asks for a ticket to track the update.
• If npm can't be reached, the generator keeps the picked version and warns.
• The template README explains the fallback.

On main nothing changes, since 8 and 9 are both published. The fallback applies on major branches after the next main merge.

Does this introduce a breaking change?

• Yes
• No

Other information

Verified by running the prompt function with mocked answers and rendering demo.html: 8 and 9 load their own version with no TODO, 10 loads 9 with the TODO, and 10 offline loads 10 with a warning.