chore: disable PostHog telemetry in development mode (#1365)

* chore: disable PostHog telemetry in development mode

Skip posthog.init() when import.meta.env.DEV is true to avoid
sending telemetry data during local development.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Apply suggestions from code review

Co-authored-by: Rin <shinohara-rin@users.noreply.github.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

docs/.vitepress/modules/posthog.ts

@@ -2,7 +2,8 @@ import posthog from 'posthog-js'
 
 import { DEFAULT_POSTHOG_CONFIG, POSTHOG_PROJECT_KEY_DOCS } from '../../../posthog.config'
 
-posthog.init(POSTHOG_PROJECT_KEY_DOCS, {
-  ...DEFAULT_POSTHOG_CONFIG,
-  // Project-specific config...
-})
+if (!import.meta.env.DEV) {
+  posthog.init(POSTHOG_PROJECT_KEY_DOCS, {
+    ...DEFAULT_POSTHOG_CONFIG,
+  })
+}