Repair materialized Node runtime launchers

[Open-Squilla]

Scope

• repair the npm and npx launchers after safe upstream symlink materialization
• run native Node, npm, and npx probes with only Runtime Pack bin directories on PATH
• advance the immutable catalog/release identity to 2026-08-21.2 / v2026.08.21.2

Branch target

main

Linked issue

None.

Release note

Runtime Pack maintenance; fixes Node Runtime Pack activation when npm/npx launchers are validated.

Verification

• python -m pytest -q — 50 passed
• python -m ruff check scripts tests
• python -m py_compile scripts/*.py tests/*.py
• actionlint
• native macOS arm64 Node pack build and Node/npm/npx probe
• OpenSquilla client extraction and Node/npm/npx probe against the rebuilt pack

Safety and compatibility

• published v2026.08.21.1 assets are not modified
• the launcher rewrite is fail-closed: it only accepts bytes matching the reviewed upstream npm CLI targets
• Windows .cmd launchers remain unchanged and are validated on native runners
• all pack probes use the isolated Runtime Pack PATH

Third-party origins

Node.js 24.19.0 remains sourced from the SHA256-pinned official nodejs.org archives declared in sources.json; no upstream version or source URL changed.