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/ofd_unix.go

@@ -0,0 +1,25 @@
+// Copyright 2026 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 unix
+
+package sqlite // import "modernc.org/sqlite"
+
+import (
+	"modernc.org/libc"
+	sqlite3 "modernc.org/sqlite/lib"
+)
+
+// ofdLocking calls the modernc_ofd_locking() gate the transpiled library
+// exports on every unix target: onoff 1 and 0 switch OFD locking on and
+// off, negative queries it; the result is the previous setting, -1 where
+// OFD locks are unavailable (every unix target but Linux always returns
+// this), -2 when the mode is frozen by an already-attempted lock. The C
+// side lives in modernc.org/libsqlite3's internal/sqlite_issue255.patch{,2}.
+func ofdLocking(onoff int32) int32 {
+	tls := libc.NewTLS()
+	defer tls.Close()
+
+	return sqlite3.Xmodernc_ofd_locking(tls, onoff)
+}