feat(frontend): add extractNumber helper

frontend/tests/csvAnalysis.test.js

@@ -3,6 +3,7 @@ import {
   parseCSV,
   getUniqueNoteValues,
   runAnalysis,
+  extractNumber,
 } from '../src/lib/csvAnalysis';
 
 // ── Fixtures ───────────────────────────────────────────────────────────────────
@@ -276,3 +277,32 @@ describe('runAnalysis — edge cases', () => {
     expect(result.consecutiveStats['Failure'].totalRuns).toBe(1);
   });
 });
+
+describe('extractNumber', () => {
+  test('extracts positive decimal from prefixed string', () => {
+    expect(extractNumber('L25.5')).toBe(25.5);
+  });
+  test('extracts negative integer with letter prefix', () => {
+    expect(extractNumber('R-12')).toBe(-12);
+  });
+  test('extracts integer from underscore-separated label', () => {
+    expect(extractNumber('trial_007')).toBe(7);
+  });
+  test('does not parse scientific notation as one number', () => {
+    // Accepted limitation: regex matches "3.2", strips "e2"
+    expect(extractNumber('3.2e2')).toBe(3.2);
+  });
+  test('strips trailing units', () => {
+    expect(extractNumber('42 ms')).toBe(42);
+  });
+  test('returns null for purely alphabetic string', () => {
+    expect(extractNumber('abc')).toBeNull();
+  });
+  test('returns null for empty string', () => {
+    expect(extractNumber('')).toBeNull();
+  });
+  test('returns null for null/undefined', () => {
+    expect(extractNumber(null)).toBeNull();
+    expect(extractNumber(undefined)).toBeNull();
+  });
+});