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/telemetry/config.ts

@@ -0,0 +1,91 @@
+import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import { homedir } from "node:os";
+import { randomUUID } from "node:crypto";
+
+// ---------------------------------------------------------------------------
+// Config directory: ~/.hyperframes/
+// ---------------------------------------------------------------------------
+
+const CONFIG_DIR = join(homedir(), ".hyperframes");
+const CONFIG_FILE = join(CONFIG_DIR, "config.json");
+
+export interface HyperframesConfig {
+  /** Whether anonymous telemetry is enabled (default: true in production) */
+  telemetryEnabled: boolean;
+  /** Stable anonymous identifier — no PII, just a random UUID */
+  anonymousId: string;
+  /** Whether the first-run telemetry notice has been shown */
+  telemetryNoticeShown: boolean;
+  /** Total CLI command invocations (for engagement prompts) */
+  commandCount: number;
+}
+
+const DEFAULT_CONFIG: HyperframesConfig = {
+  telemetryEnabled: true,
+  anonymousId: "",
+  telemetryNoticeShown: false,
+  commandCount: 0,
+};
+
+let cachedConfig: HyperframesConfig | null = null;
+
+/**
+ * Read the config file, creating it with defaults if it doesn't exist.
+ * Returns a mutable copy — call `writeConfig()` to persist changes.
+ */
+export function readConfig(): HyperframesConfig {
+  if (cachedConfig) return { ...cachedConfig };
+
+  if (!existsSync(CONFIG_FILE)) {
+    const config = { ...DEFAULT_CONFIG, anonymousId: randomUUID() };
+    writeConfig(config);
+    return config;
+  }
+
+  try {
+    const raw = readFileSync(CONFIG_FILE, "utf-8");
+    const parsed = JSON.parse(raw) as Partial<HyperframesConfig>;
+
+    const config: HyperframesConfig = {
+      telemetryEnabled: parsed.telemetryEnabled ?? DEFAULT_CONFIG.telemetryEnabled,
+      anonymousId: parsed.anonymousId || randomUUID(),
+      telemetryNoticeShown: parsed.telemetryNoticeShown ?? DEFAULT_CONFIG.telemetryNoticeShown,
+      commandCount: parsed.commandCount ?? DEFAULT_CONFIG.commandCount,
+    };
+
+    cachedConfig = config;
+    return { ...config };
+  } catch {
+    // Corrupted config — reset
+    const config = { ...DEFAULT_CONFIG, anonymousId: randomUUID() };
+    writeConfig(config);
+    return config;
+  }
+}
+
+/**
+ * Persist config to disk. Updates the in-memory cache.
+ */
+export function writeConfig(config: HyperframesConfig): void {
+  try {
+    mkdirSync(CONFIG_DIR, { recursive: true });
+    writeFileSync(CONFIG_FILE, JSON.stringify(config, null, 2) + "\n", { mode: 0o600 });
+    cachedConfig = { ...config };
+  } catch {
+    // Non-fatal — telemetry should never break the CLI
+  }
+}
+
+/**
+ * Increment the command counter and persist.
+ */
+export function incrementCommandCount(): number {
+  const config = readConfig();
+  config.commandCount++;
+  writeConfig(config);
+  return config.commandCount;
+}
+
+/** Expose the config directory path for the telemetry command output */
+export const CONFIG_PATH = CONFIG_FILE;