Externalize catalogue fundamental examples

[IzumiSy]

Motivation

The catalogue's fundamental references had many inline TS/TSX snippets that were copied directly into the generated skill docs but were not type-checked anywhere. That made the examples easy to drift out of sync with the real AppShell API, and it also duplicated some information that the examples already showed themselves.

This change moves the fundamental examples into real source files under catalogue/src/fundamental/examples/, updates the markdown to embed those files via <\!-- source: ... -->, and teaches the generator to resolve source markers for fundamental references too. With that in place, the examples now participate in catalogue type-checking instead of living as unchecked markdown-only snippets.

Design Decision

The smallest reliable approach was to keep markdown as the prose layer and make the examples the source of truth.

Instead of trying to type-check fenced markdown blocks directly, the change externalizes each TS/TSX example into a standalone file and re-embeds it during skill generation. That keeps the generated documentation readable while making the examples maintainable and verifiable. As part of that cleanup, the component reference prose drops redundant **Import:** lines so the examples themselves remain the only import source of truth.

Summary

• externalize fundamental/components.md and fundamental/design-system.md TS/TSX examples into typed source files
• resolve <\!-- source: ... --> markers for fundamental docs during catalogue skill generation
• trim redundant component reference prose and update a few stale examples to match the current AppShell API