fix(reports): stop the 'first N rows' option failing on large exports

The export path used one number for two different things: the format's hard
row cap, and the caller's explicit 'give me the first N rows'. Because
resolveExportCap() returned min(requested, formatCap) and runAll() then threw
when the result reached it, picking 'Records: First 100' in the export dialog
400'd on any report with more than 100 rows — the user asked to be truncated
and got an error instead.

Splits them: formatRowCap() is the hard, non-caller-controllable ceiling that
still throws when exceeded (a silently short file hides missing rows), while
resolveRowLimit() is the deliberate truncation and is honoured by slicing.
Verified against a 223-row dataset: limit=5 now returns 5 rows, and no limit
returns all 223.

apps/edr-freight-api/src/modules/exports/export-request.util.spec.ts

@@ -1,4 +1,10 @@
-import { EXPORT_MIME, pickByKey, resolveExportCap, resolveExportFormat } from './export-request.util';
+import {
+  EXPORT_MIME,
+  formatRowCap,
+  pickByKey,
+  resolveExportFormat,
+  resolveRowLimit,
+} from './export-request.util';
 import { CSV_ROW_CAP, PDF_ROW_CAP, XLSX_ROW_CAP } from './tabular-export.service';
 
 describe('resolveExportFormat', () => {
@@ -15,25 +21,32 @@ describe('resolveExportFormat', () => {
   });
 });
 
-describe('resolveExportCap', () => {
-  it('missing limit uses the full format cap', () => {
-    expect(resolveExportCap('xlsx', undefined)).toBe(XLSX_ROW_CAP);
-    expect(resolveExportCap('csv', undefined)).toBe(CSV_ROW_CAP);
-    expect(resolveExportCap('pdf', undefined)).toBe(PDF_ROW_CAP);
+describe('formatRowCap', () => {
+  it('is the format\'s hard ceiling and is not caller-controllable', () => {
+    expect(formatRowCap('xlsx')).toBe(XLSX_ROW_CAP);
+    expect(formatRowCap('csv')).toBe(CSV_ROW_CAP);
+    expect(formatRowCap('pdf')).toBe(PDF_ROW_CAP);
+  });
+});
+
+describe('resolveRowLimit', () => {
+  it('no limit means "everything, up to the cap"', () => {
+    expect(resolveRowLimit('xlsx', undefined)).toBeUndefined();
   });
 
-  it('a limit under the cap is used as-is', () => {
-    expect(resolveExportCap('pdf', '100')).toBe(100);
+  it('an explicit limit is the caller asking to be truncated — kept as-is', () => {
+    // Distinct from the cap: 100 here must yield 100 rows, not a 400, even
+    // when the unfiltered result is far larger.
+    expect(resolveRowLimit('pdf', '100')).toBe(100);
   });
 
-  it('a limit over the cap is clamped down', () => {
-    expect(resolveExportCap('pdf', String(PDF_ROW_CAP + 1000))).toBe(PDF_ROW_CAP);
-    expect(resolveExportCap('xlsx', String(XLSX_ROW_CAP + 1))).toBe(XLSX_ROW_CAP);
-    expect(resolveExportCap('csv', String(CSV_ROW_CAP + 1))).toBe(CSV_ROW_CAP);
+  it('an explicit limit over the format cap is clamped down', () => {
+    expect(resolveRowLimit('pdf', String(PDF_ROW_CAP + 1000))).toBe(PDF_ROW_CAP);
+    expect(resolveRowLimit('csv', String(CSV_ROW_CAP + 1))).toBe(CSV_ROW_CAP);
   });
 
-  it.each(['0', '-5', 'not-a-number', ''])('non-positive/invalid limit %p falls back to the cap', (raw) => {
-    expect(resolveExportCap('xlsx', raw)).toBe(XLSX_ROW_CAP);
+  it.each(['0', '-5', 'not-a-number', ''])('non-positive/invalid limit %p means no limit', (raw) => {
+    expect(resolveRowLimit('xlsx', raw)).toBeUndefined();
   });
 });