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/libc/strlen_nosimd.go

@@ -0,0 +1,13 @@
+// Copyright 2026 The Libc 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 || arm64 || ppc64le || s390x || riscv64 || loong64)
+
+package libc // import "modernc.org/libc"
+
+// On the remaining arches (386, arm, ...) bytes.IndexByte is a plain
+// byte loop, and the chunked IndexByte scan loses to the
+// word-at-a-time scan at every size (measured ~2x slower than even a
+// byte loop on 386), so strlen uses strlenWords there.
+const strlenUseIndexByte = false