[docs-update] Update docs for layout, navigation, and loading APIs

[github-actions]

Summary

Updates the public docs for the pending AppShell API changes around layout composition, global headers, spinner usage, command palette routing, and route metadata resolution.

Changesets that prompted this update

• .changeset/sidebar-layout-body-slot.md
• .changeset/sidebar-layout-global-top-bar.md
• .changeset/ai-chat-component.md
• .changeset/green-suns-sing.md
• .changeset/current-path-command-palette.md
• .changeset/static-meta-routes.md
• .changeset/fair-hounds-obey.md

Docs updated

• docs/components/sidebar-layout.md — documented topBar, body, useAppShellSidebar(), DynamicBreadcrumb, and the supported composition path.
• docs/components/default-sidebar.md — documented composition mode, hideHeader, hideSearch, iconRail, and low-level custom sidebar entries.
• docs/components/global-header-layout.md — added docs for the new opinionated global-header layout and GlobalHeader.
• docs/components/spinner.md — added docs for the new reusable loading indicator and its accessibility defaults.
• docs/components/command-palette.md — documented current-branch dynamic route resolution and removed a non-public customization path.
• docs/api/use-page-meta.md and docs/components/sidebar-item.md — documented literal-route precedence over dynamic siblings.
• docs/concepts/styling-theming.md and example snippets across docs/ — stopped presenting the internal astw: prefix as an app-authoring API and switched consumer examples to ordinary Tailwind utilities.
• CLAUDE.md — added the new docs pages to the documentation index.

Generated by Documentation Updater · copilot · gpt54 · 204.9 AIC · ⌖ 15.5 AIC · ⊞ 20K · ◷

[interacsean]

Superseded by #542.

That PR takes the six files here that have no counterpart on main — spinner.md, global-header-layout.md, the sidebar-layout.md body/topBar rewrite, plus default-sidebar.md, command-palette.md and use-page-meta.md — rebased onto current main and verified against source.

The other 17 files are dropped. 13 conflicted with #515, and in each one #515's text is better (<Layout gap={6}> over className="gap-6", bg-muted over bg-gray-50, and it kept the styling-boundary prose this pass deleted). The remaining four — table, timeline, tooltip, quickstart — are already equivalent on main.

The ### Documentation Index added to CLAUDE.md here is also dropped: it duplicated the convention table from #540. Worth noting this run did exactly what docs-update.md step 4 asks for — the prompt is what wants an enumerated list, and that instruction is due a follow-up fix.

Closing so the skip-if-match guard stops blocking future Documentation Updater runs.