fix(sea): patch process.dlopen in worker threads

[robertsLando]

Closes #293

Problem

Native addons fail to load from worker threads in SEA mode:

Error: The specified module could not be found.
\\?\C:\snapshot\test\node_modules\roaring\native\roaring-node-v137-win32-x64-unknown\roaring.node
  code: 'ERR_DLOPEN_FAILED'

The same code works in classic (non-SEA) pkg.

Cause

patchDlopen is what extracts a .node out of the snapshot into ~/.cache/pkg/<hash> before handing a real filesystem path to the loader. prelude/sea-bootstrap-core.js calls it once, on the main thread.

Each worker thread gets its own process object, so that patch does not carry over:

// node -e, plain Worker with eval
worker sees patched dlopen? false

prelude/sea-worker-entry.js already reapplies setupProcessPkg and patchIntlSegmenter per thread for exactly this reason — patchDlopen was just missing from the list. Workers therefore got the raw C:\snapshot\... path straight through to dlopen.

Classic pkg is unaffected because prelude/bootstrap.js runs in every thread and patches there.

Fix

One line in prelude/sea-worker-entry.js:

shared.patchDlopen(vfs.insideSnapshot);

Same fix the reporter verified in the issue.

Test

Extended test-90-sea-worker-threads rather than adding a second SEA build (each postject run costs several seconds in CI). The worker now requires a .node from the snapshot and reports whether it was extracted.

The fixture is not a real shared library, so dlopen throws in both cases — the discriminator is whether extraction happened, which only occurs when process.dlopen is patched in that thread. index.js points PKG_NATIVE_CACHE_PATH at a temp dir so nothing lands in the real ~/.cache, and main.js cleans it up.

Verified both directions on linux/node22:

• with the fix: addonExtracted:true
• with the fix reverted: addonExtracted:false, test fails

Note, not fixed here

patchChildProcess has the same shape — sea-bootstrap-core.js calls it on the main thread only, and sea-worker-entry.js does not reapply it, while classic pkg patches it in every thread. Nobody has reported it, and it needs its own test, so I left it out of this PR.

https://claude.ai/code/session_01PUj6PfkgQHcCg2bfXucBzk

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.23%. Comparing base (c1e10f5) to head (43b6220).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #297      +/-   ##
==========================================
+ Coverage   87.19%   87.23%   +0.03%     
==========================================
  Files          23       23              
  Lines        7929     7929              
  Branches     1214     1214              
==========================================
+ Hits         6914     6917       +3     
+ Misses       1008     1005       -3     
  Partials        7        7              

see 1 file with indirect coverage changes

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