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3.8 mb of sources duplicated from stage to stage and already superseded.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, 36 deletions

diff --git a/docs/history/15-o3/code/examples/mandel.zc b/docs/history/15-o3/code/examples/mandel.zc
deleted file mode 100644
index 5810397..0000000
--- a/docs/history/15-o3/code/examples/mandel.zc
+++ /dev/null
@@ -1,36 +0,0 @@
-// the mandelbrot set in 16.16 fixed point. the cpu has no fixed-point
-// multiply, so one gets wired in: a 32x32 -> 64 bit multiply, keeping the
-// middle 32 bits. the jit inlines it as two native multiplies and a shift.
-enhance fmul(a, b) micro
-	"r2 = mul a b; r3 = mulhs a b"
-	"; r3 = shl r3 16; r2 = shr r2 16; a = or r3 r2";
-
-const ONE = 65536, W = 72, H = 28, MAXIT = 40;
-let shades = " .,:;-=+*%#@";
-
-int escape(int cx, int cy) {
-	int x = 0, y = 0, i = 0;
-	while (i < MAXIT) {
-		int xx = fmul(x, x), yy = fmul(y, y);
-		if (xx + yy > 4 * ONE) return i;
-		y = 2 * fmul(x, y) + cy;
-		x = xx - yy + cx;
-		i++;
-	}
-	return MAXIT;
-}
-fn main()
-{
-	int row = 0;
-	while (row < H) {
-		int col = 0, cy = (row * 2400 / (H - 1) - 1200) * ONE / 1000;
-		while (col < W) {
-			int cx = (col * 3200 / (W - 1) - 2200) * ONE / 1000, it = escape(cx, cy);
-			putc(it == MAXIT ? '@' : shades[it * 11 / MAXIT]);
-			col++;
-		}
-		putc(10);
-		row++;
-	}
-	return 0;
-}