docs: archive the frozen stage code as one compressed tarball

docs/history kept six stages with a full copy of the project under code/,
3.8 mb of sources duplicated from stage to stage and already superseded. store
them as docs/history/code-snapshots.tar.gz, 0.66 mb, and extract one in place
to read it. every stage's notes.md stays browsable, and the index says where the
code went and how to get it back.

the top-level README points at the archive too. its other two links into
docs/history, 21-micro and 35-bench, were notes that were never kept and do not
resolve; the index now records that.

1 files changed, 0 insertions, 16 deletions

diff --git a/docs/history/13-gap-fixes/code/mkgenome.c b/docs/history/13-gap-fixes/code/mkgenome.c
deleted file mode 100644
index 8fb2cc5..0000000
--- a/docs/history/13-gap-fixes/code/mkgenome.c
+++ /dev/null
@@ -1,16 +0,0 @@
-/* turns a genome image (little-endian 32-bit words on stdin, as written by
-   tools/build.zc) into genome.h */
-#include <stdio.h>
-#define GORG 0xC0000
-int main(void)
-{
-	unsigned char b[4]; int n = 0;
-	printf("#define GORG %d\nstatic const int genome[] = {", GORG);
-	while (fread(b, 1, 4, stdin) == 4) {
-		int w = (int)(b[0] | b[1] << 8 | b[2] << 16 | (unsigned)b[3] << 24);
-		printf("%s%d", !n ? "\n" : n % 16 ? "," : ",\n", w);
-		n++;
-	}
-	printf("\n};\n#define GLEN %d\n", n);
-	return n ? 0 : 1;
-}