node-api: do not crash on module version mismatch

[krassx]

Problem

node_napi_env__::New() validates the Node-API version an add-on declares. When
the add-on requires a version this binary does not support, it throws a
descriptive error and returns nullptr:

} else if (module_api_version > NODE_API_SUPPORTED_VERSION_MAX &&
           module_api_version != NAPI_VERSION_EXPERIMENTAL) {
  node::Environment* node_env = node::Environment::GetCurrent(context);
  CHECK_NOT_NULL(node_env);
  v8impl::ThrowNodeApiVersionError(
      node_env, module_filename.c_str(), module_api_version);
  return nullptr;
}

napi_module_register_by_symbol() then dereferences that nullptr without
checking it:

napi_env env =
    node_napi_env__::New(context, module_filename, module_api_version);

napi_value _exports = nullptr;
env->CallIntoModule([&](napi_env env) {   // <-- nullptr

So loading such an add-on segfaults, and the error Node already built — "…
requires Node-API version N, but this version of Node.js only supports version M
add-ons." — is never delivered. require() cannot catch it, because the process
is gone.

Reproduction

A ten-line add-on, no third-party tooling, plain node-gyp:

#define NAPI_VERSION 99
#include <node_api.h>
static napi_value Init(napi_env env, napi_value exports) { return exports; }
NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)

$ node -e "try { require('./build/Release/hello.node') } catch (e) { console.log('caught:', e.message) }"
Segmentation fault

Confirmed on v20.x, v22.x, v24.x and v26.8.2, and main, v22.x-staging and
v24.x-staging all still lack the check.

Fix

Return when New() returns nullptr; the error it threw then propagates
normally. Verified against a local build of this branch:

$ ./out/Release/node -e "try { require('.../test_module_version_mismatch.node') }
                         catch (e) { console.log('caught:', e.message) }"
caught: file:///.../test_module_version_mismatch.node requires Node-API version
2147483646, but this version of Node.js only supports version 10 add-ons.

Removing the four added lines and relinking the same tree turns that back into
exit=139 with the catch never reached, so the new test fails without the fix
and passes with it.

node-api and js-native-api both run clean on the patched build: 102 tests,
0 failures.

Test

The error path had no coverage at all — "requires Node-API version" appears in
exactly one file in the repository, src/node_api.cc, which is how it could be
unreachable without anyone noticing. The new test is modelled on
test/node-api/test_null_init, which covers the sibling early return in the same
function.

Notes for reviewers

This is not a reprise of the Node-API versioning discussion in #57233. That
issue was closed on the grounds that the add-on had been miscompiled by a
third-party tool, which is fair — but it leaves the crash in place. The version
policy is not in question here; only that a check which already detects the
problem and writes an error should be able to deliver it. The reproduction above
involves no external tooling.

#63740 reports a superficially similar segfault in napi_register_module_v1 from
a libnode.so ABI mismatch. That is a different root cause and this change does
not address it.

Closest precedent: #58459 added CHECK_NOT_NULL(node_env) to this same function
for the node::Environment pointer. This change covers the napi_env returned
by New() twelve lines below, which is the one that is nullable by design.

Refs: #57233

AI use disclosure

Per doc/contributing/ai-guidelines.md:
this change was prepared with assistance from Claude Code. The commit
message refers to it only as "a closed-source coding agent", following the
guidance in Naming AI tools in disclosures to keep commercial brand names out
of the commit log and name them here instead.

The design, review and validation are my own. Specifically, what I verified
personally rather than taking on trust:

• The mechanism, read directly in src/node_api.cc — node_napi_env__::New()
  returns nullptr on the version-mismatch branch, and
  napi_module_register_by_symbol() dereferences it with no check. Confirmed
  under a debugger: the faulting register holds 0.
• That the fix works, against a local build of this branch, by observing the
  intended error reach a try/catch around require().
• That the new test can fail. I removed the four added lines, relinked the
  same tree, and confirmed the test fails there (exit=139, the catch never
  reached) and passes with them. A test that cannot fail would not be worth
  adding.
• That the test asserts the intended behaviour rather than the implementation's
  incidental shape: it matches the error text the version check produces, with
  the supported-version number left as \d+ so it does not need updating each
  time NODE_API_SUPPORTED_VERSION_MAX moves.
• No regressions: node-api and js-native-api run clean on the patched
  build, 102 tests, 0 failures.

I can explain and defend the change during review, and will respond to feedback
myself.

[nodejs-github-bot]

Review requested:

• @nodejs/gyp
• @nodejs/node-api

[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.21%. Comparing base (e5778f7) to head (089103e).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #66019      +/-   ##
==========================================
- Coverage   90.22%   90.21%   -0.01%     
==========================================
  Files         785      785              
  Lines      269357   269369      +12     
  Branches    51511    51507       -4     
==========================================
- Hits       243016   243010       -6     
- Misses      16853    16882      +29     
+ Partials     9488     9477      -11     

Files with missing lines	Coverage Δ
src/node_api.cc	77.07% <100.00%> (+1.73%)	⬆️

... and 33 files with indirect coverage changes

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[legendecas]

Ditto, please refrain from including impl internals in the test comments.

[krassx]

@legendecas Thank you for the review. I've applied the proposed changes.