ifc5d: match cost schedule export columns to the Bonsai cost panel (#6251)

Stefano's final ask on #6251 was specific: the ODS/XLSX export should
show exactly what the cost panel shows, ID (Identification), Name,
Quantity, Value, Total Cost, no more, no less. The previous fix in
this PR removed the internal bookkeeping columns but still exported
Description, Unit and a per-category cost breakdown (Labor Cost,
Material Cost, etc), none of which appear in the panel.

Presentation formats (.ods/.xlsx) now use an explicit allow-list of
columns instead of a block-list of internal ones, and relabel headers
to match the panel's own wording (ID / Value / Total Cost). The .csv
format is unchanged: csv2ifc still reads back the extra bookkeeping
columns for the import round trip, which is why it keeps them.

Also add a "Download CSV" button to the browser costing view
(Generate spreadsheet browser), which previously only offered a
clipboard-based Copy Selected. It reuses the already-rendered table
(respecting the user's column visibility settings) and triggers a
real file download, dropping only the UI-only Actions column.

AI-generated with Claude Code; reviewed and tested by Petru Conduraru.

src/bonsai/bonsai/bim/data/webui/static/js/utilities/costui.js

@@ -250,6 +250,14 @@ export class CostUI {
       },
     });
 
+    CostUI.addRibbonButton({
+      text: "Download CSV",
+      icon: "fa-solid fa-file-csv",
+      callback: () => {
+        CostUI.downloadCsv();
+      },
+    });
+
     CostUI.addRibbonButton({
       text: "Hide Schedules",
       icon: "fa-regular fa-eye-slash",
@@ -523,6 +531,81 @@ export class CostUI {
     }
   }
 
+  static downloadCsv() {
+    const tables = document.querySelectorAll("table[id^='cost-items-']");
+    if (tables.length === 0) {
+      alert("No cost schedule loaded to export!");
+      return;
+    }
+    tables.forEach((table) => {
+      const scheduleId = table.id.split("-").pop();
+      const csv = CostUI.tableToCsv(table);
+      if (csv === null) {
+        return;
+      }
+      const nameEl = document.querySelector(
+        "#cost-schedule-container-" + scheduleId + " .form-header span"
+      );
+      const scheduleName = nameEl
+        ? nameEl.textContent
+        : "cost_schedule_" + scheduleId;
+      CostUI.triggerCsvDownload(csv, scheduleName + ".csv");
+    });
+  }
+
+  static tableToCsv(table) {
+    const escapeCsvCell = (value) => {
+      const text = (value === null || value === undefined ? "" : value)
+        .toString()
+        .trim();
+      if (/[",\n]/.test(text)) {
+        return '"' + text.replace(/"/g, '""') + '"';
+      }
+      return text;
+    };
+
+    const cellText = (cell) => {
+      const input = cell.querySelector("input");
+      return input ? input.value : cell.innerText;
+    };
+
+    // The Actions column only holds buttons (edit/delete/etc), not data.
+    const isDataColumn = (column) => column && column !== "Actions";
+
+    const headerCells = Array.from(table.querySelectorAll("thead th")).filter(
+      (th) => isDataColumn(th.getAttribute("data-column"))
+    );
+    if (headerCells.length === 0) {
+      return null;
+    }
+
+    const rows = [headerCells.map((th) => escapeCsvCell(th.textContent)).join(",")];
+
+    table.querySelectorAll("tbody tr").forEach((row) => {
+      const cells = Array.from(row.children).filter((cell) =>
+        isDataColumn(cell.getAttribute("data-column"))
+      );
+      if (cells.length === 0) {
+        return; // e.g. the "No cost items found" placeholder row.
+      }
+      rows.push(cells.map((cell) => escapeCsvCell(cellText(cell))).join(","));
+    });
+
+    return rows.join("\n");
+  }
+
+  static triggerCsvDownload(csvContent, filename) {
+    const blob = new Blob([csvContent], { type: "text/csv;charset=utf-8;" });
+    const url = URL.createObjectURL(blob);
+    const link = document.createElement("a");
+    link.href = url;
+    link.download = filename;
+    document.body.appendChild(link);
+    link.click();
+    document.body.removeChild(link);
+    URL.revokeObjectURL(url);
+  }
+
   static createCostTable({ costSchedule, currency, callbacks }) {
     const preferences = CostUI.getColumnPreferences();
     const isScheduleOfRates = costSchedule.PredefinedType === "SCHEDULEOFRATES";