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.

e2e-tests/chat_input.spec.ts

@@ -0,0 +1,50 @@
+import { test } from "./helpers/test_helper";
+import { expect } from "@playwright/test";
+
+test("send button disabled during pending proposal", async ({ po }) => {
+  await po.setUp();
+
+  // Send a prompt that generates a proposal
+  await po.sendPrompt("Create a simple React component");
+
+  // Wait for proposal buttons to appear (ensuring proposal is rendered)
+  await expect(po.page.getByTestId("approve-proposal-button")).toBeVisible();
+
+  // Type something in the input to ensure it's not disabled due to empty input
+  await po.getChatInput().fill("test message");
+
+  // Check send button is disabled due to pending changes
+  const sendButton = po.page.getByRole("button", { name: "Send message" });
+  await expect(sendButton).toBeDisabled();
+
+  // Approve the proposal
+  await po.approveProposal();
+
+  // Check send button is enabled again
+  await expect(sendButton).toBeEnabled();
+});
+
+test("send button disabled during pending proposal - reject", async ({
+  po,
+}) => {
+  await po.setUp();
+
+  // Send a prompt that generates a proposal
+  await po.sendPrompt("Create a simple React component");
+
+  // Wait for proposal buttons to appear (ensuring proposal is rendered)
+  await expect(po.page.getByTestId("reject-proposal-button")).toBeVisible();
+
+  // Type something in the input to ensure it's not disabled due to empty input
+  await po.getChatInput().fill("test message");
+
+  // Check send button is disabled due to pending changes
+  const sendButton = po.page.getByRole("button", { name: "Send message" });
+  await expect(sendButton).toBeDisabled();
+
+  // Reject the proposal
+  await po.rejectProposal();
+
+  // Check send button is enabled again
+  await expect(sendButton).toBeEnabled();
+});