minor text updates

[JasperGilhuis]

some more text updates

[Copilot]

Pull request overview

This PR makes small UI text and formatting adjustments to improve clarity and consistency in the Copilot Token Tracker webview.

Changes:

• Updated formatCost to include a space between the dollar sign and the numeric value for cost display.
• Refined metric labels in the details webview (e.g., spelling out abbreviations and using clearer wording for cost and environmental metrics).

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
src/webview/shared/formatUtils.ts	Adjusts the formatCost helper to render cost as $ 0.1234, matching the tooltip cost formatting elsewhere.
src/webview/details/main.ts	Updates metrics table labels to more descriptive, consistent text for cost, averages, and environmental indicators.