feat(core): add built-in app info page

[IzumiSy]

Motivation

We received feedback that applications built on AppShell need a lightweight, built-in way to expose support/debug metadata such as the running AppShell version and app-specific release information.

The main use case is operational support: someone should be able to open a stable built-in page, confirm what app version/build they are looking at, and copy that information without each app having to implement its own screen.

Design Decision

The built-in page is implemented as a reserved internal route at /__appinfo instead of an auto-generated module.

This keeps the page out of the default sidebar while still letting it behave like a normal page. To make it discoverable, the Command Palette injects it into the Pages list rather than the Actions list, which keeps page-specific commands separate from contextual actions.

App-specific rows are provided through a minimal appInfo.metadata API on AppShell, limited to primitive values so consumers can format complex values themselves before rendering.

Screen shot

Page

CommandPalette

Summary

• add a built-in /__appinfo page that shows the app name, AppShell version, and app-defined metadata
• add an appInfo prop on AppShell and export the related public types
• expose the page in the Command Palette as a hidden page entry, not a sidebar item, and add a copy button for the rendered information
• add a changeset and integration coverage for the built-in page flow