nx_b64_cli.nx

nx_b64_cli.nx -- base64 a file to stdout (and optionally to a file), and DECODE a base64 file back to bytes. WHY THIS EXISTS: runtime/nx_base64.nx carries a complete b64_encode/b64_decode pair and NO main, so the capability could not be INVOKED. The encode half shipped 2026-08-06; the DECODE half stayed uninvokable -- which made base64 a one-way transport: bytes could leave the estate as text but text could not become bytes again, so binary INGEST (the rigged-donor FBX lane, 2026-08-23) had no sovereign door. This adds the missing verb by composing the SAME lib -- one codec, two verbs. BUFFER-CAP LAW (operator 2026-08-14: a ceiling that has to be guessed is a defect generator): the old BC_MAX_IN 8 MiB / BC_MAX_OUT 12 MiB REFUSED any file over 8 MiB -- a 73.6 MB donor FBX (98 MB as base64) could never pass. For FILE work there is no guess to make: sys_read_file sizes its buffer from the file, and the OUTPUT bound is ARITHMETIC from the input length (encode: 4*ceil(n/3) + newline; decode: 3*n/4). Both derived, both announced, no cap remains. usage: nx_b64_cli <infile> [outfile] encode (unchanged contract) nx_b64_cli dec <in.b64> <outfile> decode; announces bytes_in/bytes_out exit 0 ok, 1 usage, 2 unreadable/empty, 3 write-failed license_tier: ORIGINAL No hw writes (Rule 26). expect_exit: 0