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3.8 mb of sources duplicated from stage to stage and already superseded.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, 32 deletions

diff --git a/docs/history/13-gap-fixes/code/tests/joins.zc b/docs/history/13-gap-fixes/code/tests/joins.zc
deleted file mode 100644
index a272e08..0000000
--- a/docs/history/13-gap-fixes/code/tests/joins.zc
+++ /dev/null
@@ -1,32 +0,0 @@
-// joins: something given away on one path is dead afterwards, and the paths
-// that still own it free it on the way in. nothing here leaks.
-fn take(.d p) { return p[0]; }
-fn later(.d p);	// not needed any more, but still allowed
-fn mk(int v) -> *int.u { *int p = new(int); *p = v; return u*p; }
-fn count(int n) { let s = 0; switch (n % 4) { case 0: s = 10; case 1, 2: s = 20; break; default: s = 30; } return s; }
-fn main()
-{
-	let base = live_objects(), i = 0, hits = 0, k;
-	while (i < 50) {
-		let x = mk(i);
-		if (i % 3 == 0) take(d*x);	// else: freed here by the fixup
-		i++;
-	}
-	putn(live_objects() - base); putc(' ');
-	// give away and break: fine now; the normal exit frees it
-	i = 0;
-	let y = mk(7);
-	while (i < 10) { if (i == 4) { take(d*y); break; } i++; }
-	putn(live_objects() - base); putc(' ');
-	let z = mk(5);
-	while (1) { if (z[0] == 5) { hits = take(d*z); break; } }
-	putn(hits); putc(' ');
-	putn(count(0) + count(1) + count(2) + count(3)); putc(' ');
-	k = i > 3 ? i * 2 : 0 - 1;
-	putn(k); putc(' ');
-	putn(forward(new(int))); putc(' ');	// tagged and defined below: the prescan knows .d
-	**int pp; *int q = new(int); *q = 9; pp = &q; putn(**pp); free(d*q); putc(' ');
-	putn(live_objects() - base); putc(10);
-	return 0;
-}
-fn forward(*int.d p) { return 3 + *p; }