Clarify top models usage window

src/ucode/usage.py

@@ -653,7 +653,7 @@ def render_usage_summary(
             key=lambda u: (-u.total, u.name.lower()),
         )[:3]
         models_text = ", ".join(usage.name for usage in top_models)
-        lines.append(f"{label('Top models this week:')} {value(models_text)}")
+        lines.append(f"{label('Top models last 7 days:')} {value(models_text)}")
         weekly_cost = sum(
             (
                 model_usage_cost(usage, price_lookup) or Decimal(0)

tests/test_usage.py

@@ -583,7 +583,7 @@ def test_top_models_uses_per_model_token_totals(self):
         )
         # Top-models line is full names only, ranked by per-model token totals
         # (claude-opus-4 236.1K > gpt-5 13.3K > claude-haiku-4.5 920).
-        assert "Top models this week:" in result
+        assert "Top models last 7 days:" in result
         assert "claude-opus-4, gpt-5, claude-haiku-4.5" in result
         # No token counts in this line — those live in the per-model table.
         assert "236.1K" not in result