feat(ui): track solve_run analytics event

flexfoil-ui/src/components/panels/SolvePanel.tsx

@@ -17,6 +17,7 @@ import { runSweep, type SweepConfig, type SweepRunData } from '../../lib/sweepEn
 import type { PolarPoint, SweepAxis, SweepParam, ReType } from '../../types';
 import type { RunInsert } from '../../lib/storageBackend';
 import { parseSweepValues, formatSweepValues } from '../../lib/parseSweepValues';
+import { trackEvent } from '../../lib/analytics';
 
 type SolveOrCacheResult = {
   result: AnalysisResult | null;
@@ -338,6 +339,12 @@ export function SolvePanel() {
       return;
     }
 
+    trackEvent('solve_run', {
+      solve_mode: runMode === 'alpha' ? 'single_alpha' : 'single_cl',
+      solver_mode: isViscous ? 'viscous' : 'inviscid',
+      n_panels: panels.length - 1,
+    });
+
     const jobLabel = runMode === 'alpha'
       ? `${isViscous ? 'Viscous' : 'Inviscid'} @ alpha=${targetAlpha.toFixed(1)}`
       : `${isViscous ? 'Viscous' : 'Inviscid'} -> CL=${targetCl.toFixed(3)}`;
@@ -579,6 +586,12 @@ export function SolvePanel() {
 
     clearPolarSuppression();
 
+    trackEvent('solve_run', {
+      solve_mode: 'polar',
+      solver_mode: isViscous ? 'viscous' : 'inviscid',
+      n_panels: panels.length - 1,
+    });
+
     const { id: jobId, signal } = jobDispatch(
       `Polar ${alphaStart.toFixed(0)} to ${alphaEnd.toFixed(0)} (${isViscous ? 'viscous' : 'inviscid'})`
     );
@@ -724,6 +737,12 @@ export function SolvePanel() {
     const controller = new AbortController();
     sweepAbortRef.current = controller;
 
+    trackEvent('solve_run', {
+      solve_mode: sweepSecondary ? 'sweep_2d' : 'sweep_1d',
+      solver_mode: isViscous ? 'viscous' : 'inviscid',
+      n_panels: panels.length - 1,
+    });
+
     const sweepLabel = sweepSecondary
       ? `Sweep ${sweepPrimary.param} × ${sweepSecondary.param} (${isViscous ? 'viscous' : 'inviscid'})`
       : `Sweep ${sweepPrimary.param} ${sweepPrimary.start}→${sweepPrimary.end} (${isViscous ? 'viscous' : 'inviscid'})`;

flexfoil-ui/src/lib/analytics.test.ts

@@ -0,0 +1,32 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { trackEvent } from './analytics';
+
+// Tests run in the node environment, so stand up the `window` the module targets.
+const globals = globalThis as { window?: { gtag?: (...args: unknown[]) => void } };
+
+beforeEach(() => {
+  globals.window = {};
+});
+
+afterEach(() => {
+  delete globals.window;
+});
+
+describe('trackEvent', () => {
+  it('forwards the event name and params to gtag', () => {
+    const gtag = vi.fn();
+    globals.window = { gtag };
+
+    trackEvent('solve_run', { solve_mode: 'polar', solver_mode: 'viscous', n_panels: 160 });
+
+    expect(gtag).toHaveBeenCalledWith('event', 'solve_run', {
+      solve_mode: 'polar',
+      solver_mode: 'viscous',
+      n_panels: 160,
+    });
+  });
+
+  it('does not throw when the tag is blocked', () => {
+    expect(() => trackEvent('solve_run')).not.toThrow();
+  });
+});

flexfoil-ui/src/lib/analytics.ts

@@ -49,6 +49,14 @@ export function initAnalyticsConsent() {
   }
 }
 
+/**
+ * Send a custom GA4 event. Consent Mode gates delivery, so callers do not need
+ * to check consent first. gtag is absent when the tag is blocked, hence optional.
+ */
+export function trackEvent(name: string, params?: Record<string, string | number | boolean>) {
+  window.gtag?.('event', name, params);
+}
+
 declare global {
   interface Window {
     gtag?: (...args: unknown[]) => void;