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3.8 mb of sources duplicated from stage to stage and already superseded.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, 29 deletions

diff --git a/docs/history/13-gap-fixes/code/tests/enhance.zc b/docs/history/13-gap-fixes/code/tests/enhance.zc
deleted file mode 100644
index 6acc742..0000000
--- a/docs/history/13-gap-fixes/code/tests/enhance.zc
+++ /dev/null
@@ -1,29 +0,0 @@
-// custom opcodes: recipes, lifted vm code, several outputs, and a fallback
-enhance clampadd(a, b) micro "a = add a b; a = min a 100; a = max a 0";
-enhance cube(x) vm { 0 $ 0 $ * * };
-enhance divmod(a, b) -> 2 micro "r2 = sdiv a b" "\n r1 = srem a b\n r0 = r2";
-enhance div7(a) micro "a = sdiv a 7";
-enhance urem10(a) micro "a = urem a 10";
-enhance hi(a, b) micro "a = mulhu a b";
-enhance noisy(x) vm { 0 $ . } else soft_noisy;	// i/o can't be lifted, so calls use the fallback
-fn soft_noisy(x) { return x + 1; }
-let qq, rr, seed = 7;
-fn rnd() { seed = seed * 1103515245 + 12345; return seed ^ (seed >> 11); }
-fn main()
-{
-	let i = 0, a, bad = 0;
-	putn(clampadd(70, 50)); putc(' '); putn(clampadd(-50, 2)); putc(' '); putn(cube(7)); putc(' ');
-	asm { 17 5 divmod rr ! qq ! }
-	putn(qq); putc(','); putn(rr); putc(' ');
-	putn(noisy(4)); putc(' ');
-	putn(hi(-1, -1)); putc(' ');
-	while (i < 5000) {
-		a = rnd();
-		if (div7(a) != zdiv(a, 7)) bad++;
-		if (urem10(a) < 0 || urem10(a) > 9) bad++;
-		if (a / (i + 1) != zdiv(a, i + 1)) bad++;
-		i++;
-	}
-	putn(bad); putc(10);
-	return 0;
-}