Remove SetupEmscripten C++ code

[hoodmane]

Instead import setupEmscripten.ts directly. As requested by @jasnell because SetupEmscripten does not work with new module registry.

[ask-bonk]

I'm Bonk, and I've done a quick review of your PR.

This PR removes the SetupEmscripten C++ code path and instead imports setupEmscripten.ts directly as an internal module, simplifying the Emscripten initialization pipeline.

1. [HIGH] Debug print() statement left in helpers.bzl — this will produce output on every Bazel load of this file, polluting build logs.
2. [LOW] python_stdlib.zip.d.ts is now a dead file — the declare module 'pyodide-internal:generated/python_stdlib.zip' was removed but the file remains with bare top-level declarations that nothing references. Consider deleting it entirely since modules.d.ts already declares the new pyodideRuntime-internal:python_stdlib.zip module.

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This review was generated by an AI assistant and may contain inaccuracies.

[ask-bonk]

Review posted on PR #6658 with two findings:

1. [HIGH] Debug print() left in src/pyodide/helpers.bzl:284 — this will produce output on every Bazel load, polluting build logs. Posted a suggestion to remove it.

2. [LOW] src/pyodide/types/python_stdlib.zip.d.ts is now a dead file — the module declaration was removed but the file remains with bare top-level declarations that nothing references. Suggested deleting it since modules.d.ts already declares the new pyodideRuntime-internal:python_stdlib.zip module.

The rest of the PR looks clean: all SetupEmscripten/EmscriptenRuntime references are fully removed, the C++ deletion is complete, the Bazel module type reclassifications (data -> internal/wasm) are correct, and the TypeScript signature change from sync to async loadPyodide is properly awaited at the call site.

github run

[codspeed-hq]

Merging this PR will not alter performance

✅ 72 untouched benchmarks
⏩ 129 skipped benchmarks¹

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_{Comparing hoodmane/remove-emscripten-setup (98ad560) with main (f75a8ae)}

Footnotes

1. 129 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[danlapid]

Goodbye old friend - you will not be missed

[ryanking13]

I don't have the exact context of why it was existed in C++ originally, but the change looks good overall.

[dom96]

I wonder if there are other things we can remove now that SetupEmscripten is gone.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.56%. Comparing base (b2e22f4) to head (98ad560).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6658      +/-   ##
==========================================
- Coverage   66.57%   66.56%   -0.02%     
==========================================
  Files         403      402       -1     
  Lines      115958   115889      -69     
  Branches    19416    19404      -12     
==========================================
- Hits        77198    77137      -61     
+ Misses      27182    27180       -2     
+ Partials    11578    11572       -6     

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