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3.8 mb of sources duplicated from stage to stage and already superseded.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, 27 deletions

diff --git a/docs/history/15-o3/code/examples/repl.zc b/docs/history/15-o3/code/examples/repl.zc
deleted file mode 100644
index b7b81b8..0000000
--- a/docs/history/15-o3/code/examples/repl.zc
+++ /dev/null
@@ -1,27 +0,0 @@
-// a repl on the resident compiler: each backtick-separated chunk of input is
-// compiled as a function body and run. definitions (fn ...) can be loaded too:
-// a chunk that starts with "fn" goes through load instead of eval.
-let buf[4000];
-fn readchunk()
-{
-	let n = 0, c;
-	while (!eof()) {
-		c = getc();
-		if (c == 96) break;
-		if (n < 3999) { buf[n] = c; n++; }
-	}
-	buf[n] = 0;
-	return n;
-}
-fn main()
-{
-	let q, i;
-	while (!eof()) {
-		readchunk();
-		q = tokens(buf);
-		if (q[0] && q[1] == T_ID && q[2] == intern("fn")) load(q);
-		else eval(q);
-		free(d*q);
-	}
-	return 0;
-}