fix: feuille xlsx vide editable avec quadrillage vierge BUG-094

backend/xlsx_reader.py

@@ -32,6 +32,13 @@ logger = logging.getLogger("obsigate.xlsx_reader")
 MAX_ROWS = 500
 MAX_COLS = 40
 
+# BUG-094 — an empty sheet used to render as a bare "Feuille vide" paragraph
+# with no cell at all, so a freshly added sheet had nothing to click and no way
+# to insert a row/column. Render a small blank grid instead (Excel-like), with
+# real A1 coordinates, so the cells are editable and the structure actions work.
+EMPTY_SHEET_ROWS = 20
+EMPTY_SHEET_COLS = 8
+
 # #153 A9 — window size served by ``read_sheet_window()`` (lazy per-sheet
 # loading). The endpoint is bounded so a single request can never ask for the
 # whole workbook back in one JSON payload; the UI pages through the rest.
@@ -424,6 +431,10 @@ def render_sheets(file_path: Path) -> list[dict[str, Any]]:
     sheets = []
     for i, title in enumerate(titles):
         grid = _trim(formulas[i])
+        # BUG-094 — a blank sheet still needs an editable grid (see constants):
+        # the viewer's cell editing and structure actions all hang off a cell.
+        if not grid:
+            grid = [[""] * EMPTY_SHEET_COLS for _ in range(EMPTY_SHEET_ROWS)]
         # The shadow grid is NOT trimmed independently: _trim drops the
         # trailing empty columns of each grid on its own width, which would
         # shift every cached value left of its formula. Indexing it