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/builder.json

@@ -0,0 +1,6 @@
+{
+	"autogen": "<none>",
+	"autotag": "<none>",
+	"autoupdate": "<none>",
+	"test": "darwin/(amd64|arm64)|freebsd/(amd64|arm64|386|arm$)|linux/(386|amd64|arm|arm64|loong64|ppc64le|riscv64|s390x)|netbsd/amd64|openbsd/(amd64|arm64)|windows/(amd64|arm64|386)"
+}