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3.8 mb of sources duplicated from stage to stage and already superseded.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, 38 deletions

diff --git a/docs/history/17-o3-boundaries/code/examples/primes.zc b/docs/history/17-o3-boundaries/code/examples/primes.zc
deleted file mode 100644
index 26df0b5..0000000
--- a/docs/history/17-o3-boundaries/code/examples/primes.zc
+++ /dev/null
@@ -1,38 +0,0 @@
-// primes below 60000: an o3 sieve over a fixed array, the primes
-// gathered into a growable one, then a few questions asked of them.
-// with ZYTRACE=1 the o3 lines show each region being lifted and compiled.
-
-// marks the composites; f[i] ends up 1 for every prime i
-o3 int sieve(fixed []int f)
-{
-	int n = len(f), c = 0;
-	for (int i = 2; i < n; i++) f[i] = 1;
-	for (int i = 2; i * i < n; i++)
-		if (f[i]) for (int j = i * i; j < n; j += i) f[j] = 0;
-	for (int i = 2; i < n; i++) c += f[i];
-	return c;
-}
-// the largest gap between neighbours, and where it starts
-o3 int gap(fixed []int f, *int at)
-{
-	int n = len(f), last = 2, best = 0, where = 0;
-	for (int i = 3; i < n; i++)
-		if (f[i]) { if (i - last > best) { best = i - last; where = last; } last = i; }
-	*at = where;
-	return best;
-}
-fn main()
-{
-	fixed []int f = new(fixed []int, 60000);
-	[]int ps = new([]int);
-	int c = sieve(f), at = 0, twins = 0;
-	for (int i = 2; i < len(f); i++) if (f[i]) push(ps, i);
-	o3 { for (int k = 1; k < len(ps); k++) if (ps[k] - ps[k - 1] == 2) twins++; }
-	puts("primes below 60000: "); putn(c); putc(10);
-	puts("the last five:"); for (int k = len(ps) - 5; k < len(ps); k++) { putc(' '); putn(ps[k]); } putc(10);
-	puts("twin pairs: "); putn(twins); putc(10);
-	int g = gap(f, &at);
-	puts("widest gap: "); putn(g); puts(", after "); putn(at); putc(10);
-	free(d*f); free(d*ps);
-	return 0;
-}