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/mathutil/sqr_std.go

@@ -0,0 +1,10 @@
+//go:build riscv64 || loong64
+// +build riscv64 loong64
+
+package mathutil
+
+func (f *float) sqr() {
+	f.n.Mul(f.n, f.n)
+	f.fracBits *= 2
+	f.normalize()
+}