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3.8 mb of sources duplicated from stage to stage and already superseded.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/17-o3-boundaries/code/examples/dump.zc b/docs/history/17-o3-boundaries/code/examples/dump.zc
deleted file mode 100644
index 6082213..0000000
--- a/docs/history/17-o3-boundaries/code/examples/dump.zc
+++ /dev/null
@@ -1,32 +0,0 @@
-// printing any struct with no printing code: the heap knows each object's
-// type, and reflection walks its fields
-struct person { *char name; int age; };
-struct item { *char name; int count; *person owner; };
-
-fn dump(p)
-{
-	let t = typeof_obj(p), i = 0;
-	if (!t) { puts("?"); return 0; }
-	tprint(t); puts(" { ");
-	while (i < tnfields(t)) {
-		let ft = tftype(t, i), v = p[tfoff(t, i)];
-		if (i) puts(", ");
-		puts(tfname(t, i)); puts(": ");
-		if (tkind(ft) == TY_PTR && telem(ft) == typeof(char)) { putc('"'); puts(v); putc('"'); }
-		else if (tkind(ft) == TY_PTR) { if (v) dump(v); else puts("null"); }
-		else putn(v);
-		i++;
-	}
-	puts(" }");
-	return 0;
-}
-fn main()
-{
-	*person ana = new(person);
-	ana.name = "ana"; ana.age = 30;
-	*item lamp = new(item);
-	lamp.name = "lamp"; lamp.count = 3; lamp.owner = ana;
-	dump(lamp); putc(10);
-	free(d*lamp);
-	return 0;
-}