Returns the CSS class for the token usage indicator based on the current
total, the configured warning threshold, and the assumed context window size.
Yellow band: [threshold, contextWindowSize). Red band: [contextWindowSize, ∞).
Parameters
totalTokens: number
threshold: number
contextWindowSize: number = CHAT_CONTEXT_WINDOW_SIZE
Returns the CSS class for the token usage indicator based on the current total, the configured warning threshold, and the assumed context window size. Yellow band: [threshold, contextWindowSize). Red band: [contextWindowSize, ∞).