chore: make custom metrics more obviously clickable

[typpo]

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[gru-agent]

TestGru Assignment

Summary

Link	CommitId	Status	Reason
Detail	7b45173	🚫 Skipped	No files need to be tested {"src/app/src/pages/eval/components/CustomMetrics.css":"target file(src/app/src/pages/eval/components/CustomMetrics.css) not in work scope \n include: src \n exclude: node_modules,/*.test.ts,/.test.tsx,**/.spec.ts,/*.spec.tsx,/.d.ts,**/.test.js,/*.spec.js,src/app/src","src/app/src/pages/eval/components/CustomMetrics.tsx":"target file(src/app/src/pages/eval/components/CustomMetrics.tsx) not in work scope \n include: src \n exclude: node_modules,/.test.ts,**/.test.tsx,/*.spec.ts,/.spec.tsx,**/.d.ts,/*.test.js,/*.spec.js,src/app/src"}

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[gru-agent]

TestGru Assignment

Summary

Link	CommitId	Status	Reason
Detail	7b45173	🚫 Skipped	No files need to be tested {"src/app/src/pages/eval/components/CustomMetrics.css":"target file(src/app/src/pages/eval/components/CustomMetrics.css) not in work scope \n include: src/app/src//*.ts \n exclude: node_modules,/.test.ts,**/.test.tsx,/*.spec.ts,/.spec.tsx,**/.d.ts,/*.test.js,/.spec.js","src/app/src/pages/eval/components/CustomMetrics.tsx":"target file(src/app/src/pages/eval/components/CustomMetrics.tsx) not in work scope \n include: src/app/src/**/.ts \n exclude: node_modules,/*.test.ts,/.test.tsx,**/.spec.ts,/*.spec.tsx,/.d.ts,**/.test.js,**/*.spec.js"}

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[ellipsis-dev]

The metric rendering logic is duplicated between the tooltip and non-tooltip branches. Consider extracting the common rendering code into a helper function to improve maintainability.