fix(router): Wrap root error/404 components in HTML shell - #1226

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Source-audit review found a blocking document regression and a mismatch with the installed Router contract.

Evidence:

• In @tanstack/react-router@1.170.16, MatchView renders the root shellComponent outside the route catch and not-found boundaries. The existing ShellComponent therefore already wraps root errorComponent and notFoundComponent output.
• On the PR preview, a direct request to /source-audit-definitely-missing produces 2 html, 2 head, and 2 body elements. The second html is nested under a div. It also duplicates script and shell output. The same request on current production has exactly 1 of each document element.
• If the original exception starts inside ShellComponent, changing the route error component cannot catch it because that catch boundary is inside the shell. The Router global catch outside the shell still renders its own built-in ErrorComponent, not RootErrorBoundary.

Please hold this PR. Inspect the first exception and component stack before the reported HierarchyRequestError, then fix that source. If the first exception is inside ShellComponent, either make that shell path safe or address the full-document global fallback contract upstream in Router. Do not nest a second document inside the existing root shell.