The sandboxed Pyodide host (used when ENABLE_PYODIDE_FILE_PERSISTENCE is
disabled, the default) embeds its script in a String.raw template. The
matplotlib show() override was written with '\\t' escapes as if in a normal
string context, but String.raw preserves them verbatim, so the iframe's
script parser turns them into literal backslash-t characters in the
generated Python source. Pyodide then fails to compile any code that
triggers the matplotlib patch with "SyntaxError: unexpected character
after line continuation character", which is why matplotlib only worked
with the file persistence worker path enabled.
Use single '\t' escapes instead: String.raw keeps them as-is in the
script text and the sandbox's JS parser produces real tab indentation,
matching the working implementation in pyodide.worker.ts.
Fixes#26660
Classic298