feat: DuckDB quantiles in-process (gcc CGO), not Ladybug. (#34)

OQ3: internal/duckstats + bin/qa/stats.go. Zig stays Ladybug-only.
mikefarah/yq for small structured slices. Gitea #30.

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/arran4/golang-ical v0.3.5
 	github.com/chewxy/math32 v1.11.2
 	github.com/daulet/tokenizers v1.27.0
+	github.com/duckdb/duckdb-go/v2 v2.10505.0
 	github.com/go-git/go-git/v5 v5.19.2
 	golang.org/x/sys v0.47.0
 	golang.org/x/text v0.40.0
@@ -20,10 +21,17 @@ require (
 	github.com/apache/arrow-go/v18 v18.6.0 // indirect
 	github.com/cloudflare/circl v1.6.3 // indirect
 	github.com/cyphar/filepath-securejoin v0.6.1 // indirect
+	github.com/duckdb/duckdb-go-bindings v0.10505.0 // indirect
+	github.com/duckdb/duckdb-go-bindings/lib/darwin-amd64 v0.10505.0 // indirect
+	github.com/duckdb/duckdb-go-bindings/lib/darwin-arm64 v0.10505.0 // indirect
+	github.com/duckdb/duckdb-go-bindings/lib/linux-amd64 v0.10505.0 // indirect
+	github.com/duckdb/duckdb-go-bindings/lib/linux-arm64 v0.10505.0 // indirect
+	github.com/duckdb/duckdb-go-bindings/lib/windows-amd64 v0.10505.0 // indirect
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/emirpasic/gods v1.18.1 // indirect
 	github.com/go-git/gcfg v1.5.1-0.20230307220236-3a3c6141e376 // indirect
 	github.com/go-git/go-billy/v5 v5.9.0 // indirect
+	github.com/go-viper/mapstructure/v2 v2.5.0 // indirect
 	github.com/goccy/go-json v0.10.6 // indirect
 	github.com/golang/groupcache v0.0.0-20241129210726-2c02b8208cf8 // indirect
 	github.com/google/flatbuffers v25.12.19+incompatible // indirect