[stevekaliski-stripe]

The Linux ARM64 standalone CLI built by Node 26.13.0 can fail before startup on 16/64 KiB-page kernels because the built-in SEA injector produces incompatible ELF load mappings. This is tracked in nodejs/node#67048.

Use Node's documented preparation-blob + postject flow for Linux ARM64. Pin the matching Node producer/runtime to 26.13.0 and postject to 1.0.0-alpha.6. Other platforms retain the built-in SEA builder. Linux CI runs the resulting executables with --version/--help, records kernel/page size, and uploads binaries and checksums for validation on the target host.

Validation:

• The external-postject candidate passed --version and --help on native ARM64 Linux with 4 KiB pages in https://github.com/stripe/link-cli/actions/runs/43042758509 (the later VM-tool installation was cancelled after Ubuntu DNS failures).
• Independent static inspection passed 4/16/64 KiB offset/address congruence and nonoverlapping load mappings, and verified the SEA payload and exported-symbol GNU-hash lookups.
• Frozen offline installation and workflow YAML/shell checks pass.
• Native 64 KiB-kernel validation remains pending: the standard ubuntu-24.04-arm runner reports 4096-byte pages, and the matching runner label/group still needs to be identified. This PR stays draft until that target-environment check is available.