docs: add agent bootstrap and contract read router

rules/patterns/import-export/README.md

@@ -11,3 +11,31 @@ Canonical file transfer UX patterns for Go web applications:
 This pattern covers UI and UX contracts. Business-specific validation and file schemas remain in
 the host project's own architecture docs.
 
+## Export Handler Sketch
+
+```go
+func ExportCSV(c *gin.Context) {
+    c.Header("Content-Type", "text/csv; charset=utf-8")
+    c.Header("Content-Disposition", `attachment; filename="export.csv"`)
+    c.Writer.Write([]byte{0xEF, 0xBB, 0xBF})
+
+    w := csv.NewWriter(c.Writer)
+    w.Comma = ';'
+    w.Write([]string{"ID", "Name", "Price"})
+
+    err := svc.StreamRows(ctx, filters, func(row Row) error {
+        return w.Write([]string{row.ID, row.Name, formatPrice(row.Price)})
+    })
+    w.Flush()
+    if err != nil {
+        slog.Error("csv export failed mid-stream", "err", err)
+    }
+}
+```
+
+## Locale Notes
+
+- BOM avoids broken UTF-8 in Excel on Windows.
+- Semicolon avoids single-column imports in RU/EU locales.
+- Decimal comma keeps numbers numeric in Excel.
+- `DD.MM.YYYY` is preferred over ISO dates for user-facing spreadsheet exports.