fix(vector): answer project-filtered queries with two searches (#70)

A project filter was '(project = ? OR scope = global)', which vec0 rejects in a nearest-neighbour query ('A LIMIT or k = ? constraint is required'). The only caller that passes a project is the de-duplication of new observations, which treats an error as 'insert', so semantic de-duplication never took effect.

Run one search for the project and one for global documents and merge them by distance without repeats, cut to the limit. QueryMultiField asks for enough field documents and keeps the best per observation; its two skipped tests are enabled. Because de-duplication now runs, canMergeInto skips a superseded or deleted note as a merge target.

Co-authored-by: Claude Sonnet 5.5 <[email protected]>

internal/worker/sdk/dedup_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"testing"
 
+	"github.com/lukaszraczylo/claude-mnemonic/internal/db/gorm"
 	"github.com/lukaszraczylo/claude-mnemonic/internal/vector/sqlitevec"
 	"github.com/lukaszraczylo/claude-mnemonic/pkg/models"
 )
@@ -142,3 +143,35 @@ func TestCheckVectorDeduplication_EmptySearchText(t *testing.T) {
 		t.Errorf("expected Action='insert' for empty observation, got %q", result.Action)
 	}
 }
+
+func TestCanMergeInto(t *testing.T) {
+	ctx := context.Background()
+	dir := t.TempDir()
+	store, err := gorm.NewStore(gorm.Config{Path: dir + "/test.db", MaxConns: 1})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer store.Close()
+	obsStore := gorm.NewObservationStore(store, nil, nil, nil)
+	id, _, err := obsStore.StoreObservation(ctx, "s1", "proj", &models.ParsedObservation{Type: models.ObsTypeDiscovery, Title: "A note"}, 1, 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	p := &Processor{observationStore: obsStore}
+
+	if !p.canMergeInto(ctx, id) {
+		t.Error("a live observation is a merge target")
+	}
+	if p.canMergeInto(ctx, id+1000) {
+		t.Error("an observation that does not exist is not")
+	}
+	if err := store.DB.Exec(`UPDATE observations SET is_superseded = 1 WHERE id = ?`, id).Error; err != nil {
+		t.Fatal(err)
+	}
+	if p.canMergeInto(ctx, id) {
+		t.Error("a superseded observation is hidden from sessions, so nothing is merged into it")
+	}
+	if !(&Processor{}).canMergeInto(ctx, id) {
+		t.Error("without an observation store there is nothing to check against")
+	}
+}