Make the dictionary startup line report rows, not capabilities

It logged dictionary.Langs(), which is a compile-time constant of the languages
DreamDict *supports*. The database deployed until today supported Spanish and
contained none of it, so the line printed a confident "[en fr pt-PT es zh]"
over a file where every Spanish lookup came back empty — the exact failure the
line exists to catch, reported as success.

Contents() counts rows per language instead. For a file somebody has to copy
onto the box by hand, "what is in it" is the only question worth asking, and
the answer is now en=136615 es=102971 fr=56096 pt-PT=136300 zh=120883.

Claude-Session: https://claude.ai/code/session_016y6gyuHkQXPiEuW8RGQyua

internal/lexicon/dreamdict_test.go

@@ -519,3 +519,25 @@ func TestHandlerDecodesPunctuatedWords(t *testing.T) {
 		t.Errorf("Word = %q, want the decoded word", res.Word)
 	}
 }
+
+func TestContentsCountsRowsNotSupportedLanguages(t *testing.T) {
+	// The fixture is seeded with English and pt-PT only. DreamDict *supports*
+	// French, Spanish and Chinese too — and a startup line that reported the
+	// supported set would have named all five while every French lookup came
+	// back empty. That is the failure this log line exists to catch, so it must
+	// count rows.
+	got := NewSet(openFixture(t))
+	summary := got.Contents()
+	if !strings.Contains(summary, "en=") || !strings.Contains(summary, "pt-PT=") {
+		t.Errorf("Contents = %q, want the languages the fixture actually holds", summary)
+	}
+	for _, absent := range []string{"fr=", "es=", "zh="} {
+		if strings.Contains(summary, absent) {
+			t.Errorf("Contents = %q, must not name %q — no rows exist for it", summary, absent)
+		}
+	}
+	// No dictionary at all still has to answer something printable.
+	if s := NewSet(nil).Contents(); s == "" {
+		t.Error("Contents with no dictionary must still say something")
+	}
+}