Restore pdwidgets to the frozen wasm runtime

Tonight's rebuild silently dropped it: cmods/pdwidgets, the symlink the freeze
loop looks for, had been removed in an earlier session to make room on an MCU
build and never restored. cmods/manifest-micropython.py includes a sibling only
if its directory exists, so the module vanished from the interpreter with no
build-time signal at all.

Caught by the wasm-verifier sweep: the /pdwidgets/ hero threw
"ImportError: no module named pdwidgets", and the two binaries differ 292 -> 0
on `strings | grep ^pdwidgets/`. Now 292 again.

Only the hero broke because hero-runtime.js hardcodes one
mip.install("pydevices-desktop") and relied on the freeze; the gallery installs
?deps= explicitly and never did.

Author: bdbarnett