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/CONTRIBUTORS

@@ -0,0 +1,15 @@
+# This file lists people who contributed code to this repository.  The AUTHORS
+# file lists the copyright holders; this file lists people.
+#
+# Names should be added to this file like so:
+#     Name <email address>
+#
+# Please keep the list sorted.
+
+Bodecker DellaMaria <bojdell@gmail.com>
+Edward Betts <edward@4angle.com>
+Faiz Abbasi <faizamodo@gmail.com>
+Gary Burd <gary@beagledreams.com>
+Jan Mercl <0xjnml@gmail.com>
+Muhammad Surya <surya.asriadie@gmail.com>
+Santiago De la Cruz <delacruzsantiago12@gmail.com>