fix: standardize file parameter naming across all tools

- Change `relevant_files` to `files` in debug_issue tool
- Change `reference_files` to `files` in think_deeper tool
- Now all tools consistently use `files` parameter name
- Fix cross-platform test for Windows path separators
- Update README to reflect consistent parameter naming

This improves API consistency and reduces confusion when using different tools.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

README.md

@@ -289,7 +289,7 @@ All tools that work with files support **both individual files and entire direct
 **`debug_issue`** - Debug with file context
 - `error_description`: Description of the issue (required)
 - `error_context`: Stack trace or logs
-- `relevant_files`: Files or directories related to the issue
+- `files`: Files or directories related to the issue
 - `runtime_info`: Environment details
 - `previous_attempts`: What you've tried
 
@@ -301,7 +301,7 @@ All tools that work with files support **both individual files and entire direct
 - `current_analysis`: Your current thinking (required)
 - `problem_context`: Additional context
 - `focus_areas`: Specific aspects to focus on
-- `reference_files`: Files or directories for context
+- `files`: Files or directories for context
 
 ```
 "Use gemini to think deeper about my design with reference to the src/models/ directory"