* Add MCP activation + usage PostHog events and North Star dashboard prompt
- mcp:authorize_success (server) on OAuth consent completion
- mcp:tool_call (server) on every MCP tool invocation, with tool/success/
error_code/client_id and mcp_client vs in_app_agent source
- mcp:consent_viewed / mcp:consent_denied on the OAuth consent page
- mcp:setup_url_copy / mcp:setup_command_copy intent events on /ai
- docs/posthog-north-star-dashboard.md: prompt to configure the PostHog
core-actions dashboard (activation rate, MCP setup funnel, daily MCP users)
* Fix codex review findings: count schema-rejected MCP calls as failures, wrap audit tools
- mcp:tool_call now fires after output validation; schema mismatches report
success:false with MCP_OUTPUT_VALIDATION (the SDK surfaces them to the
client as JSON-RPC errors)
- run_site_audit/get_audit_status/get_audit_issues/get_audit_pages were
registered without instrumentMcpToolHandler, so their usage and failures
were invisible
* Remove dashboard prompt doc