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/README

@@ -0,0 +1,10 @@
+This is a goinstall-able mirror of modified code already published at:
+http://git.nic.cz/redmine/projects/gornd/repository
+
+Packages in this repository:
+
+Install: $ go get modernc.org/mathutil
+Godocs:  http://godoc.org/modernc.org/mathutil
+
+Install: $ go get modernc.org/mathutil/mersenne
+Godocs:  http://godoc.org/modernc.org/mathutil/mersenne