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/memory/memory64.go

@@ -0,0 +1,10 @@
+// Copyright 2018 The Memory 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 amd64 || amd64p32 || arm64 || arm64be || mips64 || mips64le || mips64p32 || mips64p32le || ppc64 || ppc64le || sparc64 || riscv64 || loong64
+// +build amd64 amd64p32 arm64 arm64be mips64 mips64le mips64p32 mips64p32le ppc64 ppc64le sparc64 riscv64 loong64
+
+package memory // import "modernc.org/memory"
+
+type rawmem [1<<50 - 1]byte