fix(core): restore Tailwind theme bridge from styles export

[IzumiSy]

Motivation

A regression reported in discussion #311 showed that consumer-authored Tailwind utilities such as bg-card, border-border, and text-muted-foreground stopped resolving after @tailor-platform/app-shell/theme.css was turned into a no-op compatibility shim.

The tricky part is that we now have consumers in both states: some still import theme.css, while others removed it after the shim release. We need to restore the Tailwind v4 theme bridge for both groups without making theme.css meaningful again.

Design Decision

Keep the public @tailor-platform/app-shell/theme.css export as the current no-op compatibility shim, and instead make @tailor-platform/app-shell/styles the single real entrypoint for consumer styling.

To do that, this PR turns styles into a thin raw CSS wrapper that imports:

• the real theme source (which includes the Tailwind bridge), and
• the precompiled AppShell component stylesheet.

The precompiled stylesheet is renamed to app-shell-core.css so app-shell.css can become that wrapper. This preserves compatibility for apps that either kept or removed the legacy theme.css import.

Summary

• add a public app-shell.css wrapper and shared theme.bridge.css bridge source
• rename the generated compiled stylesheet to app-shell-core.css and keep the internal build pointed at the shared bridge
• add a patch changeset and validate with package build, type-check, lint, and test

[pkg-pr-new]

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pnpm add https://pkg.pr.new/tailor-platform/app-shell/@tailor-platform/app-shell@6c4c875

pnpm add https://pkg.pr.new/tailor-platform/app-shell/@tailor-platform/app-shell-sdk-plugin@6c4c875

pnpm add https://pkg.pr.new/tailor-platform/app-shell/@tailor-platform/app-shell-vite-plugin@6c4c875

commit: 6c4c875