fix(desktop): force rebuild when packaged app is missing node-pty native binary (closes #62462)

[Snowdchike]

Summary

hermes desktop on Linux could silently launch a packaged Electron app whose pty.node was missing, then crash in the main process with Cannot find module pty.node. The content-hash stamp only proved the source tree was unchanged — it did NOT verify the packaged artifact actually carried a usable native binary, so a previously-built (but broken) artifact could satisfy the stamp forever.

This adds two layers of defense at build-time so the failure surfaces as a loud rebuild, not a runtime crash.

Root cause

The user's reported behavior matches exactly what happens when both:

• prebuilds/linux-x64/ is empty (no matching prebuild for Electron's Node ABI), AND
• build/Release/ is empty (@electron/rebuild was never run)

…because both paths fall through, node-pty ships into the package with its JS surface intact but no .node binary, and Electron dies loading unixTerminal.js at startup.

The existing stamp check in _desktop_build_needed() would happily mark the broken package "up to date (content stamp matches)" because the source tree hadn't changed since the broken build was produced.

Changes

apps/desktop/scripts/stage-native-deps.mjs — fail loud, not silent

• New validation step that throws when both build/Release/ and prebuilds/<platform>-<arch>/ lack a *.node binary or spawn-helper.
• Error message points to the exact remediation: npx @electron/rebuild -w node-pty --platform <p> --arch <a>.

hermes_cli/main.py — native-deps gate alongside content stamp

• New _desktop_native_deps_present() checks the same paths node-pty's loader checks (build/Release/, prebuilds/-/) plus lib/index.js for defensive coverage.
• New _native_arch_suffix() returns the canonical <platform>-<arch> dir name (linux-x64, linux-arm64, darwin-arm64, win32-x64, …) without duplicating the lookup logic in 5 places.
• New _desktop_unpacked_resources_root() centralizes how we locate app.asar.unpacked/.../resources/dist/node_modules/node-pty — stays in sync with _desktop_packaged_executable.
• _desktop_build_needed() now returns True when native deps are missing, forcing a rebuild.

tests/hermes_cli/test_gui_command.py — coverage

• _make_packaged_executable helper updated to stage realistic node-pty payload (lib/index.js + build/Release/pty.node) by default; with_native_deps=False opt-out for the missing-deps test.
• 4 new tests: missing native binary forces rebuild even with fresh stamp; prebuild-only layout is accepted; lib/index.js regression is caught; arch-suffix mapping covers linux/darwin/win32.

Verification

$ ./venv/bin/python -m pytest tests/hermes_cli/test_gui_command.py -v
============================== 65 passed in 1.13s ==============================

End-to-end smoke test of the mjs change confirmed the new validation throws with the expected error message when both build/Release/ and prebuilds/linux-x64/ are empty.

Notes

• Sir's machine has the binary at the correct path (apps/desktop/release/linux-unpacked/resources/app.asar.unpacked/dist/node_modules/node-pty/build/Release/pty.node) — this only affects installs where the staging step produced an incomplete payload.
• The fix is conservative: it does NOT modify electron-builder config, asarUnpack, or before-pack.mjs. Those would be a larger change touching every platform's packaging flow. This PR isolates the change to: (1) fail loud during staging, and (2) detect + rebuild at the CLI gate.

Closes #62462

[alt-glitch]

This was generated by AI during triage.

Related to #61798 (competing/complementary fix for the same missing-pty.node Linux Desktop crash family — that PR makes @electron/rebuild traverse the workspace root to produce the binary; this PR validates the packaged artifact and forces a rebuild when it's absent), #62462 (the bug this closes), and #62171 (bug spec). Different mechanisms — a maintainer should pick which layer to take (or both).