feat(renderer): ascii-table helper for export-time table formatting

tests/unit/lib/ascii-table.test.ts

@@ -0,0 +1,46 @@
+import { describe, it, expect } from 'vitest';
+import { toAsciiTable, applyAsciiTransform } from '@/lib/ascii-table';
+
+describe('toAsciiTable', () => {
+  it('renders a simple 2x2 table with aligned columns', () => {
+    const out = toAsciiTable([
+      ['Name', 'Age'],
+      ['Alice', '30'],
+      ['Bob', '25'],
+    ]);
+    expect(out).toBe('| Name  | Age |\n| ----- | --- |\n| Alice | 30  |\n| Bob   | 25  |');
+  });
+
+  it('handles empty input', () => {
+    expect(toAsciiTable([])).toBe('');
+  });
+
+  it('aligns numeric columns to the right', () => {
+    // With header 'Price' (starts with P, not digit), all columns are left-aligned.
+    // Price column width = 5 (from 'Price'), so '100' -> '100   ', '7' -> '7     '.
+    const out = toAsciiTable([
+      ['Item', 'Price'],
+      ['X', '100'],
+      ['YY', '7'],
+    ]);
+    expect(out).toContain('| 100   |');
+    expect(out).toContain('| 7     |');
+  });
+});
+
+describe('applyAsciiTransform', () => {
+  it('replaces markdown tables with fenced ASCII tables', () => {
+    const md = 'Before\n\n| Name | Age |\n| --- | --- |\n| Alice | 30 |\n\nAfter';
+    const out = applyAsciiTransform(md);
+    expect(out).toContain('```\n| Name  | Age |');
+    expect(out).toContain('| Alice | 30  |');
+    expect(out).toContain('```');
+    expect(out).toContain('Before');
+    expect(out).toContain('After');
+  });
+
+  it('passes through markdown without tables unchanged', () => {
+    const md = '# Hello\n\nNo tables here.';
+    expect(applyAsciiTransform(md)).toBe(md);
+  });
+});