[codex] Skip Windows Node 26 until MSVC build flags are fixed

[yanyiwu]

Summary

• Keep Node 26 CI coverage on Linux, ARM Linux, and macOS.
• Exclude only the windows-latest + 26.x matrix entry from test and release workflows.
• Document the Windows Node 26 blocker in the workflow matrix.

Context

The Node 22/24/26 matrix update landed on master, but the test workflow failed only on build (26.x, windows-latest) during npm ci. The fallback source build reaches MSVC, then fails because Node 26.3.0 headers inject clang ThinLTO options into the generated Visual Studio project:

cl : warning D9002: ignoring unknown option '-flto=thin'
LINK : warning LNK4044: unrecognized option '/flto=thin'; ignored
LINK : fatal error LNK1117: syntax error in option 'opt:lldltojobs=2'

The other 11 matrix entries passed. An attempted local binding.gyp flag removal and npm_config_force_process_config workaround did not prevent node-gyp from reading the Node 26 header common.gypi on Windows, so this PR uses a narrow matrix exclusion until the upstream Node/node-gyp/MSVC flag handling is fixed.

Validation

• GitHub Actions test matrix on this PR.