add .gitignore, clean up generated files from node_modules

Remove from tracking:
- dist/ (build output, regenerated by bun run build.ts)
- node_modules/.pnpm/ (pnpm internal store, 247MB)
- node_modules/.bin/ (executable symlinks)
- node_modules/.ignored/ and .ignored_* (source-map dirs moved aside by pnpm)
- 100 pnpm-installed package symlinks (regenerated by pnpm install)

Keep in tracking:
- Private package stubs not on npm (color-diff-napi, modifiers-napi,
  @ant/claude-for-chrome-mcp, @anthropic-ai/mcpb, @anthropic-ai/sandbox-runtime)
- Source-map extracted packages not installed by pnpm (@grpc/*, @protobufjs/*, etc.)

claude-code-source/node_modules/@azure/msal-node/dist/crypto/HashUtils.mjs

@@ -1,21 +0,0 @@
-/*! @azure/msal-node v3.8.1 2025-10-29 */
-'use strict';
-import { Hash } from '../utils/Constants.mjs';
-import crypto from 'crypto';
-
-/*
- * Copyright (c) Microsoft Corporation. All rights reserved.
- * Licensed under the MIT License.
- */
-class HashUtils {
-    /**
-     * generate 'SHA256' hash
-     * @param buffer
-     */
-    sha256(buffer) {
-        return crypto.createHash(Hash.SHA256).update(buffer).digest();
-    }
-}
-
-export { HashUtils };
-//# sourceMappingURL=HashUtils.mjs.map