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3.8 mb of sources duplicated from stage to stage and already superseded.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/15-o3/code/examples/life.zc b/docs/history/15-o3/code/examples/life.zc
deleted file mode 100644
index a43d660..0000000
--- a/docs/history/15-o3/code/examples/life.zc
+++ /dev/null
@@ -1,38 +0,0 @@
-// conway's life on a 10 x 20 torus, with typed 2d arrays in a struct.
-// a glider walks diagonally and wraps around the edges.
-const H = 10, W = 20;
-struct board { [10][20]int c; };
-
-int get(*board b, int y, int x) { return b.c[(y + H) % H][(x + W) % W]; }
-fn step(*board from, *board to)
-{
-	for (int y = 0; y < H; y++)
-		for (int x = 0; x < W; x++) {
-			int n = 0;
-			for (int dy = 0 - 1; dy <= 1; dy++)
-				for (int dx = 0 - 1; dx <= 1; dx++)
-					if (dy || dx) n += get(from, y + dy, x + dx);
-			to.c[y][x] = n == 3 || (n == 2 && from.c[y][x]);
-		}
-	return 0;
-}
-fn show(*board b, int gen)
-{
-	puts("generation "); putn(gen); putc(10);
-	for (int y = 0; y < H; y++) { for (int x = 0; x < W; x++) putc(b.c[y][x] ? '#' : '.'); putc(10); }
-	return 0;
-}
-fn main()
-{
-	*board a = new(board), b = new(board);
-	a.c[0][1] = 1; a.c[1][2] = 1; a.c[2][0] = 1; a.c[2][1] = 1; a.c[2][2] = 1;
-	// two generations a pass, a -> b -> a: owned boards can't be swapped
-	// through a temporary, since the analyzer can't follow that
-	for (int g = 0; g <= 40; g += 2) {
-		if (g % 20 == 0) show(a, g);
-		step(a, b);
-		step(b, a);
-	}
-	free(d*a); free(d*b);
-	return 0;
-}