SEA binary size findings and safe Node.js build flags

About 94.5% of the standalone binary is Node.js. Fossilize strips the copied runtime before postject injection, reducing linux-x64 from roughly 125 MiB to 108 MiB raw and 34 MiB to 30 MiB gzip. UPX is rejected because it destroys ELF notes. The largest custom-build saving is --with-intl=small-icu (~26–28 MiB); --without-inspector, --without-amaro, --v8-disable-maglev, and --enable-lto provide smaller gains. Never use --with-intl=none, --without-ssl, --without-lief, --without-sqlite, --disable-single-executable-application, or --v8-lite-mode: they break required CLI/SEA behavior or severely hurt performance. Custom builds remain deferred because five native runners and ~3.5-hour cold builds offer poor value versus ~5-minute fossilize builds; Darwin cross-compilation from Linux is unsupported.