Performance: define baseline metrics and profiling workflow

[dlrice]

Goal

• Create a repeatable way to measure performance improvements.

Scope

• Define baseline scenarios and how to reproduce them
• Choose profiling tools (browser perf tools, lighthouse, custom perf marks, etc.)
• Record baseline results for comparison later

Acceptance criteria

• Documented workflow for capturing metrics
• Baseline numbers captured and stored (issue comment or repo doc)

[minjoonkim]

found tachometer, which we might be able to use for benchmark testing
https://github.com/google/tachometer