feat: Enhance replace tool reliability with multi-stage edit correction

This commit significantly improves the `replace` tool's robustness by introducing a multi-stage correction mechanism. This directly addresses challenges with LLM-generated tool inputs, particularly the over-escaping of strings sometimes observed with Gemini models, and other minor discrepancies that previously led to failed edits.

The correction process is as follows:
1.  **Targeted Unescaping:** The system first applies a specialized unescaping function to the `old_string` and `new_string` to counteract common LLM-induced escaping patterns.
2.  **LLM-Powered Discrepancy Resolution:** If a unique match for the `old_string` is still not found, the system leverages a Gemini model (`gemini-2.5-flash-preview-04-17`) to:
    *   Identify the most probable intended `old_string` in the file by intelligently correcting minor formatting or escaping differences.
    *   Adjust the `new_string` to correspond with any corrections made to the `old_string`, maintaining the original edit's intent.

This enhancement makes the `replace` tool more resilient and effective, leading to a higher success rate for automated code modifications. The `expected_replacements` parameter has been removed as the tool now focuses on finding a single, unique, and correctable match. The tool's description and error reporting have been updated to reflect these new capabilities.

Fixes https://b.corp.google.com/issues/416933027

packages/server/src/config/config.ts

@@ -148,7 +148,7 @@ function createToolRegistry(config: Config): ToolRegistry {
     new ReadFileTool(targetDir),
     new GrepTool(targetDir),
     new GlobTool(targetDir),
-    new EditTool(targetDir),
+    new EditTool(config),
     new WriteFileTool(targetDir),
     new WebFetchTool(), // Note: WebFetchTool takes no arguments
     new ReadManyFilesTool(targetDir),