feat(cli): add opt-out anonymous telemetry via PostHog

Add anonymous usage telemetry to help improve the CLI. Uses PostHog's
HTTP batch API directly (zero new dependencies) with a 5-second timeout
and fail-silent behavior — telemetry never breaks the CLI.

What's collected: command names, render performance (duration, fps,
quality), template choices, OS/arch/Node version/CLI version.

What's NOT collected: file paths, project names, video content, or
any personally identifiable information.

Telemetry is:
- Disabled in dev mode (running via tsx)
- Disabled in CI (CI=true) or via HYPERFRAMES_NO_TELEMETRY=1
- Disabled when API key is placeholder (safe to merge before key is set)
- Controllable via `hyperframes telemetry [enable|disable|status]`
- Disclosed on first run with clear opt-out instructions

Config stored at ~/.hyperframes/config.json (0600 permissions).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/cli/src/commands/browser.ts

@@ -9,6 +9,7 @@ import {
   CHROME_VERSION,
   CACHE_DIR,
 } from "../browser/manager.js";
+import { trackBrowserInstall } from "../telemetry/events.js";
 
 async function runEnsure(): Promise<void> {
   clack.intro(c.bold("hyperframes browser ensure"));
@@ -47,6 +48,7 @@ async function runEnsure(): Promise<void> {
   });
 
   downloadSpinner.stop(c.success("Download complete"));
+  trackBrowserInstall(true);
 
   console.log();
   console.log(`   ${c.dim("Source:")}  ${c.bold(result.source)}`);