p2: digest with in-sift FIFO, SQLite caches, Honcho context, recover

Dixie is capped (max_inflight 2, queue_depth 8, queue_wait 20s) and
never queued on llama-server. Streaming chat, thinking off, 45s
fallback to clean. Digest and chunk-embedding caches are
content-addressed SQLite (Honcho context is not cached). Recover
uses the guarded Fetcher. guardian-star is refused in code.

vendor/modernc.org/sqlite/rulimit.go

@@ -0,0 +1,19 @@
+// Copyright 2021 The Sqlite Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux || darwin || netbsd || openbsd
+// +build linux darwin netbsd openbsd
+
+package sqlite // import "modernc.org/sqlite"
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+func setMaxOpenFiles(n int64) error {
+	var rLimit unix.Rlimit
+	rLimit.Max = uint64(n)
+	rLimit.Cur = uint64(n)
+	return unix.Setrlimit(unix.RLIMIT_NOFILE, &rLimit)
+}