misc/github-copilot-cli: Add script and binary flavors

script flavor (default): existing behavior with all npm dependencies
binary flavor (-bin): C launcher binary with all JS and Node.js
embedded in the binary, requires only node at runtime
(no Node.js, no npm packages, no native modules)

Node.js SEA (Single Executable Application) cannot be used because
postject_find_resource() has no FreeBSD code path. The binary flavor
instead uses a C launcher that embeds all copilot JS files as a gzip-
compressed tar archive, extracts to ~/.cache/github-copilot-cli/v<ver>/
on first run, and executes them with the system node.