Optimize media manager polling and product info retrieval

- Remove recursive polling in MediaManager.html; context is now loaded once at startup.
- Optimize getSelectedProductInfo in mediaHandlers.ts to reduce SpreadsheetApp API calls.
- Update related tests to match new optimization.

src/mediaHandlers.ts

@@ -17,14 +17,34 @@ export function showMediaManager() {
 
 export function getSelectedProductInfo(): { sku: string, title: string } | null {
   const ss = new GASSpreadsheetService()
+
+  // Optimization: Direct usage to avoid multiple service calls overhead
+  // Use SpreadsheetApp only once if possible to get active context
   const sheet = SpreadsheetApp.getActiveSheet()
   if (sheet.getName() !== "product_inventory") return null
 
   const row = sheet.getActiveRange().getRow()
   if (row <= 1) return null // Header
 
-  const sku = ss.getCellValueByColumnName("product_inventory", row, "sku")
-  const title = ss.getCellValueByColumnName("product_inventory", row, "title")
+  // Optimization: Get the whole row values in one go
+  // We need to know which index is SKU and Title.
+  // Getting headers once is cheaper than searching by name twice if we cache or just linear scan once.
+  // Actually, getCellValueByColumnName does: getSheet -> getHeaders (read) -> getRowData (read).
+  // Doing it twice = 6 operations.
+  // Let's do it manually efficiently:
+
+  const headers = sheet.getRange(1, 1, 1, sheet.getLastColumn()).getValues()[0] as string[];
+  const skuIdx = headers.indexOf("sku");
+  const titleIdx = headers.indexOf("title");
+
+  if (skuIdx === -1) return null; // No SKU column
+
+  // Read the specific row
+  // getRange(row, 1, 1, lastCol)
+  const rowValues = sheet.getRange(row, 1, 1, sheet.getLastColumn()).getValues()[0];
+
+  const sku = rowValues[skuIdx];
+  const title = titleIdx !== -1 ? rowValues[titleIdx] : "";
 
   return sku ? { sku: String(sku), title: String(title || "") } : null
 }