Scratch file path violated the project rule 'scratch files go in
.sx-tmp/, never /tmp'. Route the temp .bin through the repo-local,
gitignored .sx-tmp/ dir, creating it at runtime via create_dir_all
(mirroring 0713) so the test is self-contained on a clean checkout.
Digest assertions and output are unchanged.
Make the SHA-256 digest path allocation-free (foundation heap-discipline):
- final() and sha256_hex() now return the 64-char lowercase hex digest as
a [64]u8 by value on the stack; the cstring(64) heap allocation is gone.
- sha256_file() streams the file in fixed 64KB stack chunks via open_file/
File.read/File.close (defer-closed on every path) instead of slurping it
with read_file; peak memory is O(chunk), not O(filesize).
Tests (compare via a zero-copy string view over the [64]u8):
- 0710 updated to the by-value API (output unchanged).
- 0711 known-answer vectors: "", "abc", NIST-56/112, padding boundaries
{0,55,56,57,63,64,65,119,120}, and 1000 / 1,000,000 'a' repeats, each
pinned to its published digest (cross-checked with shasum -a 256).
- 0712 streaming equivalence (one-shot == byte-at-a-time == split-mid-block
== split-on-boundary) plus sha256_file(temp) == in-memory digest.
src/ untouched. zig build && zig build test && tests/run_examples.sh green.
