feat(tui): add link picker and navigation history

Press [ in detail view to open link picker showing all [[links]]
in the current entry. Enter follows a link, resolving by title
then body substring. Navigation history stack enables esc to pop
back through followed links before returning to list.

Adds Store.ResolveLink() for non-transactional link resolution
from the TUI layer.

internal/db/links.go

@@ -55,6 +55,26 @@ func syncLinks(ctx context.Context, tx *sql.Tx, s *Store, entityID string, body
 	return nil
 }
 
+func (s *Store) ResolveLink(ctx context.Context, linkText string) (*Entity, error) {
+	lower := strings.ToLower(linkText)
+
+	var id string
+	err := s.db.QueryRowContext(ctx, `
+		SELECT id FROM entities
+		WHERE LOWER(title) = ? AND deleted_at IS NULL
+		ORDER BY created_at DESC LIMIT 1`, lower).Scan(&id)
+	if err != nil {
+		err = s.db.QueryRowContext(ctx, `
+			SELECT id FROM entities
+			WHERE LOWER(body) LIKE ? AND deleted_at IS NULL
+			ORDER BY created_at DESC LIMIT 1`, "%"+lower+"%").Scan(&id)
+	}
+	if err != nil {
+		return nil, ErrNotFound
+	}
+	return s.Get(ctx, id)
+}
+
 func (s *Store) LoadBacklinks(ctx context.Context, entityID string) ([]Backlink, error) {
 	rows, err := s.db.QueryContext(ctx, `
 		SELECT e.id, e.title, e.body, el.link_text

internal/db/links_test.go

@@ -223,3 +223,50 @@ func TestSyncLinks_DeletedSourceHidden(t *testing.T) {
 		t.Fatalf("soft-deleted source should not appear in backlinks, got %d", len(backlinks))
 	}
 }
+
+func TestResolveLink_TitleMatch(t *testing.T) {
+	s := testStore(t)
+	ctx := context.Background()
+
+	title := "nginx config"
+	target := &Entity{Body: "proxy_pass details", Title: &title, Glyph: "note", Tags: []string{}}
+	if err := s.Create(ctx, target); err != nil {
+		t.Fatal(err)
+	}
+
+	resolved, err := s.ResolveLink(ctx, "nginx config")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if resolved.ID != target.ID {
+		t.Errorf("resolved ID = %s, want %s", resolved.ID, target.ID)
+	}
+}
+
+func TestResolveLink_BodyFallback(t *testing.T) {
+	s := testStore(t)
+	ctx := context.Background()
+
+	target := &Entity{Body: "deploy staging checklist", Glyph: "note", Tags: []string{}}
+	if err := s.Create(ctx, target); err != nil {
+		t.Fatal(err)
+	}
+
+	resolved, err := s.ResolveLink(ctx, "deploy staging")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if resolved.ID != target.ID {
+		t.Errorf("resolved ID = %s, want %s", resolved.ID, target.ID)
+	}
+}
+
+func TestResolveLink_NotFound(t *testing.T) {
+	s := testStore(t)
+	ctx := context.Background()
+
+	_, err := s.ResolveLink(ctx, "nonexistent entry")
+	if err != ErrNotFound {
+		t.Errorf("expected ErrNotFound, got %v", err)
+	}
+}