feat: implement fuzzy search and replace functionality with Levenshtein distance

- Added `applySearchReplace` function to handle search and replace operations with fuzzy matching capabilities.
- Introduced tests for various scenarios including fuzzy matching with typos, exact matches, and handling whitespace differences.
- Created a parser for search/replace blocks to facilitate the new functionality.
- Updated prompts for search-replace operations to clarify usage and examples.
- Added utility functions for text normalization and language detection based on file extensions.
- Implemented a minimal stdio MCP server for local testing with tools for adding numbers and printing environment variables.

testing/README.md

@@ -0,0 +1,50 @@
+### Fake stdio MCP server
+
+This directory contains a minimal stdio MCP server for local testing.
+
+- **Tools**:
+  - **calculator_add**: adds two numbers. Inputs: `a` (number), `b` (number).
+  - **print_envs**: returns all environment variables visible to the server as pretty JSON.
+
+### Requirements
+
+- **Node 20+** (same as the repo engines)
+- Uses the repo dependency `@modelcontextprotocol/sdk` and `zod`
+
+### Launch
+
+- **Via Node**:
+
+  ```bash
+  node testing/fake-stdio-mcp-server.mjs
+  ```
+
+- **Via script** (adds a stable entrypoint path):
+
+  ```bash
+  testing/run-fake-stdio-mcp-server.sh
+  ```
+
+### Passing environment variables
+
+Environment variables provided when launching (either from your shell or by the app) will be visible to the `print_envs` tool.
+
+```bash
+export FOO=bar
+export SECRET_TOKEN=example
+testing/run-fake-stdio-mcp-server.sh
+```
+
+### Integrating with Dyad (stdio MCP)
+
+When adding a stdio MCP server in the app, use:
+
+- **Command**: `testing/run-fake-stdio-mcp-server.sh` (absolute path recommended)
+- **Transport**: `stdio`
+- **Args**: leave empty (not required)
+- **Env**: optional key/values (e.g., `FOO=bar`)
+
+Once connected, you should see the two tools listed:
+
+- `calculator_add`
+- `print_envs`