fix(kbsearch): rank FTS correctly, filter before -n, start the daemon. (#5)

Go search took worst BM25 hits (ORDER BY score), cut to -n before --root,
and never called ensureDaemon. Ranking and flag parsing move to a cgo-free
package so CI can fail those regressions without ladybug. --hop errors
instead of being swallowed into the query.

bin/kbsearch/rank/rank_test.go

@@ -0,0 +1,143 @@
+// Unit tests for ranking/filtering and CLI parsing (no db, no model, offline).
+package rank
+
+import (
+	"strings"
+	"testing"
+)
+
+func h(id, root, source string) Hit {
+	return Hit{ID: id, Text: id, Root: root, Source: source}
+}
+
+func ids(hits []Hit) []string {
+	out := make([]string, len(hits))
+	for i, hit := range hits {
+		out[i] = hit.ID
+	}
+	return out
+}
+
+func eq(t *testing.T, got []Hit, want ...string) {
+	t.Helper()
+	g := ids(got)
+	if len(g) != len(want) {
+		t.Fatalf("got %v, want %v", g, want)
+	}
+	for i := range want {
+		if g[i] != want[i] {
+			t.Fatalf("got %v, want %v", g, want)
+		}
+	}
+}
+
+// A facts leaf that ranks below the limit in the unfiltered list must still
+// be returned for --root facts. Filtering after truncation loses it.
+func TestRankAndFilterFiltersBeforeLimit(t *testing.T) {
+	fts := []Hit{
+		h("i1", "info", "docs/a.md"),
+		h("i2", "info", "docs/b.md"),
+		h("i3", "info", "docs/c.md"),
+		h("f1", "facts", "docker ps x compose"),
+	}
+	eq(t, RankAndFilter(fts, nil, "facts", "", 2), "f1")
+}
+
+func TestRankAndFilterRepoFiltersBeforeLimit(t *testing.T) {
+	fts := []Hit{
+		h("a", "info", "eSlider/2dph:README.md"),
+		h("b", "info", "eSlider/2dph:PLAN.md"),
+		h("c", "info", "eSlider/ops:compose.yaml"),
+	}
+	eq(t, RankAndFilter(fts, nil, "", "ops", 2), "c")
+}
+
+func TestRankAndFilterTruncatesToLimit(t *testing.T) {
+	fts := []Hit{h("a", "info", "x"), h("b", "info", "x"), h("c", "info", "x")}
+	eq(t, RankAndFilter(fts, nil, "", "", 2), "a", "b")
+}
+
+func TestRankAndFilterLimitZeroKeepsAll(t *testing.T) {
+	fts := []Hit{h("a", "info", "x"), h("b", "info", "x")}
+	eq(t, RankAndFilter(fts, nil, "", "", 0), "a", "b")
+}
+
+func TestHybridFusesBothRetrievers(t *testing.T) {
+	fts := []Hit{h("only-fts", "info", "x"), h("both", "info", "x")}
+	vec := []Hit{h("only-vec", "info", "x"), h("both", "info", "x")}
+	eq(t, Hybrid(fts, vec, 0), "both", "only-fts", "only-vec")
+}
+
+func TestHybridTiesAreDeterministic(t *testing.T) {
+	fts := []Hit{h("b", "info", "x"), h("a", "info", "x")}
+	first := ids(Hybrid(fts, nil, 0))
+	for i := 0; i < 50; i++ {
+		got := ids(Hybrid(fts, nil, 0))
+		for j := range first {
+			if got[j] != first[j] {
+				t.Fatalf("unstable order: %v then %v", first, got)
+			}
+		}
+	}
+}
+
+func TestHybridKeepsVectorScoreForSharedHit(t *testing.T) {
+	fts := []Hit{{ID: "x", Root: "info", Score: 0}}
+	vec := []Hit{{ID: "x", Root: "info", Score: 0.87}}
+	got := Hybrid(fts, vec, 0)
+	if len(got) != 1 || got[0].Score != 0.87 {
+		t.Fatalf("got %+v, want score 0.87", got)
+	}
+}
+
+// The old parser dropped unknown flags and appended their arguments to the
+// query, so `search "q" --hop 1` searched for "q 1". --hop is not implemented
+// here (needs File edges); it must still fail closed instead of changing q.
+func TestParseHopIsNotSwallowedIntoTheQuery(t *testing.T) {
+	_, err := ParseArgs([]string{"what runs on arc-2", "--hop", "1"})
+	if err == nil {
+		t.Fatal("expected --hop to error (not implemented), not be swallowed")
+	}
+	if !strings.Contains(err.Error(), "--hop") {
+		t.Fatalf("error should name --hop, got %v", err)
+	}
+}
+
+func TestParseRejectsUnknownFlags(t *testing.T) {
+	if _, err := ParseArgs([]string{"query", "--nope"}); err == nil {
+		t.Fatal("unknown flag accepted")
+	}
+}
+
+func TestParseRejectsBadValues(t *testing.T) {
+	for _, args := range [][]string{
+		{"q", "-n", "zero"},
+		{"q", "-n", "0"},
+		{"q", "--root", "nonsense"},
+		{"q", "--hop"},
+		{"--json"},
+	} {
+		if _, err := ParseArgs(args); err == nil {
+			t.Errorf("accepted %v", args)
+		}
+	}
+}
+
+func TestParseDefaults(t *testing.T) {
+	opt, err := ParseArgs([]string{"two", "words", "--json"})
+	if err != nil || opt.Query != "two words" || opt.Limit != 20 || !opt.JSONOut {
+		t.Fatalf("got %+v err=%v", opt, err)
+	}
+}
+
+func TestListModelNeedsNoQuery(t *testing.T) {
+	if _, err := ParseArgs([]string{"--list-model"}); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestFTSQueryOrdersByScoreDescending(t *testing.T) {
+	if !strings.Contains(FTSStmt, "ORDER BY score DESC") {
+		t.Fatalf("FTS query must order by score DESC, got:\n%s", FTSStmt)
+	}
+}