Rename Go package from posthog to insights across all 80+ files.
Consumers now import as `insights "github.com/hanzoai/insights-go"`
and use insights.Client, insights.Config, insights.Capture, etc.
- Rename posthog.go -> insights.go, posthog_test.go -> insights_test.go
- Update package declaration from posthog to insights in all .go files
- Update SDKName from posthog-go to insights-go
- Update DefaultEndpoint from app.posthog.com to insights.hanzo.ai
- Update all FieldError/ConfigError type strings
- Update User-Agent headers, log prefixes, comments, and docs
- Update JSON test fixtures to match new SDK name
- Update CLI, examples, extras, and sdk_compliance_adapter
- Fix pre-existing go vet warnings (non-constant format strings)
zeekay
