## Summary
This PR fixes an issue where the browserToolEnabled setting was not correctly affecting the system prompt generation, causing the browser functionality to either always be included or always be excluded regardless of user preference.

## Issue Details
When users toggled the "Enable Browser Tools" setting (browserToolEnabled) in the settings panel, this change was not properly reflected in the system prompt. The root cause was in the `generateSystemPrompt` function, which was only considering the model's capability (`supportsComputerUse`) but not checking the user's preference from state (`browserToolEnabled`).

## Technical Analysis
The issue occurred because:

1. The `generateSystemPrompt` function wasn't retrieving the `browserToolEnabled` setting from state
2. It was passing only the model capability check (`apiConfiguration.openRouterModelInfo?.supportsComputerUse`) to the `SYSTEM_PROMPT` function
3. This meant the user setting had no effect on the system prompt generation

This is a pattern we need to watch for in the codebase - any place where we need to check both:
- Model capability (from `getCurrentCline()` or `apiConfiguration`)
- User preference (from state)

## Fix Implementation
The fix:
1. Retrieves the `browserToolEnabled` setting from state in `generateSystemPrompt`
2. Creates a combined check: `canUseBrowserTool = (apiConfiguration.openRouterModelInfo?.supportsComputerUse ?? false) && (browserToolEnabled ?? true)`
3. Passes this combined value to `SYSTEM_PROMPT`

This ensures that browser tools are only enabled when BOTH the model supports computer use AND the user has enabled browser tools.

## Additional Improvements
- Added proper error handling and fallbacks in the telemetry properties collection to handle undefined Cline instances
- Improved the pattern for accessing model capabilities through apiConfiguration when no Cline instance exists

## Testing
- Added tests that directly verify the `canUseBrowserTool` computation in various scenarios
- Added integration tests to verify the entire flow from setting changes to system prompt generation

These test improvements should catch similar issues in the future.