e2e: performance metrics reporting

[BrodyHughes]

Fixes BX-1876

Overview

Adds comprehensive performance testing infrastructure to track and monitor extension
performance metrics across builds.

Key Features

• Performance Metrics Collection: Tracks DOM load times, React render times, memory
  usage, and user flow durations
• Baseline Comparison System: Compares metrics against established baselines with
  configurable warning (20%) and critical (50%) thresholds
• CI Integration: Automated performance tests run on PRs with results displayed in
  GitHub Actions summary
• Visual Status Indicators: Clear ✅/⚠️/❌ emoji indicators for quick performance
  assessment

What's Measured

• domContentLoaded - Time to DOM ready
• firstMeaningfulPaint - Time to first visual content
• loadScripts - Script loading duration
• firstReactRender - React initial render time
• uiStartup - Total UI initialization time
• flowDuration - Complete user flow timing (e.g., wallet import)
• memoryUsage - JS heap memory consumption

Implementation Details

• Passive performance collection only when IS_TESTING=true to avoid interfering with
  extension initialization
• Consolidated metrics table for easy scanning
• Automatic baseline generation from actual test runs via yarn
  perf:generate-baseline
• Tests for cold start, warm reload, and wallet import flows

Scripts Added

• yarn perf:test - Run performance tests locally
• yarn perf:generate-baseline - Generate baseline from current metrics
• yarn perf:update-baseline - Update baseline after performance improvements

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PR-Codex overview

This PR introduces performance testing for the extension, adding metrics collection and reporting capabilities to monitor the startup and user flow performance, along with baseline generation for future comparisons.

Detailed summary

• Added performance testing configuration in vitest.config.ts.
• Created performance test scripts in e2e-performance-tests.sh.
• Introduced performance metrics interfaces in types.ts.
• Implemented performance metrics collection in index.ts and popup/index.ts.
• Added baseline JSON structure in baseline.json.
• Developed performance test cases in initialLoad.test.ts and walletFlowPerformance.test.ts.
• Created scripts for generating and updating performance baselines.
• Integrated performance reporting in GitHub Actions workflows.

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[linear]

BX-1876 Add performance metrics in end-to-end testing