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/utils/EncodingUtils.mjs

@@ -1,51 +0,0 @@
-/*! @azure/msal-node v3.8.1 2025-10-29 */
-'use strict';
-import { EncodingTypes, Constants } from '@azure/msal-common/node';
-
-/*
- * Copyright (c) Microsoft Corporation. All rights reserved.
- * Licensed under the MIT License.
- */
-class EncodingUtils {
-    /**
-     * 'utf8': Multibyte encoded Unicode characters. Many web pages and other document formats use UTF-8.
-     * 'base64': Base64 encoding.
-     *
-     * @param str text
-     */
-    static base64Encode(str, encoding) {
-        return Buffer.from(str, encoding).toString(EncodingTypes.BASE64);
-    }
-    /**
-     * encode a URL
-     * @param str
-     */
-    static base64EncodeUrl(str, encoding) {
-        return EncodingUtils.base64Encode(str, encoding)
-            .replace(/=/g, Constants.EMPTY_STRING)
-            .replace(/\+/g, "-")
-            .replace(/\//g, "_");
-    }
-    /**
-     * 'utf8': Multibyte encoded Unicode characters. Many web pages and other document formats use UTF-8.
-     * 'base64': Base64 encoding.
-     *
-     * @param base64Str Base64 encoded text
-     */
-    static base64Decode(base64Str) {
-        return Buffer.from(base64Str, EncodingTypes.BASE64).toString("utf8");
-    }
-    /**
-     * @param base64Str Base64 encoded Url
-     */
-    static base64DecodeUrl(base64Str) {
-        let str = base64Str.replace(/-/g, "+").replace(/_/g, "/");
-        while (str.length % 4) {
-            str += "=";
-        }
-        return EncodingUtils.base64Decode(str);
-    }
-}
-
-export { EncodingUtils };
-//# sourceMappingURL=EncodingUtils.mjs.map