fix: restore full-width source inventory

CHANGELOG.md

@@ -26,6 +26,9 @@
 - Made the frontend dataset client exhaust canonical 200-row pages. Real
   Waterinfo persistence pushed the regional project beyond the old 50-row
   default and exposed that older sources otherwise disappeared from the UI.
+- Restored the source inventory as a full-width, naturally flowing overview
+  band after the premium desktop grid rules had compressed it into a narrow,
+  internally scrolling column.
 
 ## Sprint 202 Source intelligence, full evolution metrics and local assistant (2026-07-15)
 

backend/tests/test_sprint203_waterinfo_history.py

@@ -142,3 +142,12 @@ def test_frontend_loads_all_dataset_pages_after_temporal_import_expansion() -> N
     assert "DATASET_PAGE_SIZE = 200" in client
     assert "offset < (total ?? 0)" in client
     assert "items.length !== total" in client
+
+
+def test_source_inventory_remains_full_width_after_premium_desktop_rules() -> None:
+    styles = (ROOT / "frontend" / "src" / "styles" / "premium.css").read_text(encoding="utf-8")
+
+    final_rule = styles.rsplit(".workspace-grid-data > section.source-catalog-panel", maxsplit=1)[1]
+    assert "grid-column: 1 / -1" in final_rule
+    assert "max-height: none" in final_rule
+    assert "overflow: visible" in final_rule

docs/CODEX_EXECUTION_LOG.md

@@ -8483,3 +8483,9 @@ Validation evidence:
 Remaining operational step:
 - Redeploy the pagination correction and verify complete source visibility plus
   the historical overlay through the LAN browser.
+
+Final live UI correction:
+- Browser inspection at 1280x720 found the premium desktop grid overriding the
+  source catalog's full-width placement and constraining it to a 282px internal
+  scroller. A final, component-specific CSS rule restores the catalog as a
+  full-width overview band without changing the remaining data-workspace grid.

frontend/src/styles/premium.css

@@ -2008,3 +2008,10 @@ details.ai-lab-model-surface > summary strong {
     grid-template-columns: repeat(2, minmax(0, 1fr));
   }
 }
+
+/* The source inventory is an overview band, not one of the scrollable data tools. */
+.workspace-grid-data > section.source-catalog-panel {
+  grid-column: 1 / -1;
+  max-height: none;
+  overflow: visible;
+}