feat: Add context tokens to environment details

Adds the current conversation's context token count to the environment details section by:
- Using existing getApiMetrics() to retrieve contextTokens from the last API request
- Adding a new "Context Tokens" section between "Current Time" and "Current Mode"
- Formatting the token count with toLocaleString() for better readability
- Showing "(Not available)" when no context tokens are present

This provides visibility into the current conversation's token usage directly in the environment details, helping track context window utilization.

src/core/Cline.ts

@@ -3041,6 +3041,10 @@ export class Cline {
 		const timeZoneOffsetStr = `${timeZoneOffset >= 0 ? "+" : ""}${timeZoneOffset}:00`
 		details += `\n\n# Current Time\n${formatter.format(now)} (${timeZone}, UTC${timeZoneOffsetStr})`
 
+		// Add context tokens information
+		const { contextTokens } = getApiMetrics(this.clineMessages)
+		details += `\n\n# Current Context Size (Tokens)\n${contextTokens ? contextTokens.toLocaleString() : "(Not available)"}`
+
 		// Add current mode and any mode-specific warnings
 		const { mode, customModes } = (await this.providerRef.deref()?.getState()) ?? {}
 		const currentMode = mode ?? defaultModeSlug