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/@aws-crypto/crc32/build/main/aws_crc32.js

@@ -1,31 +0,0 @@
-"use strict";
-// Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
-// SPDX-License-Identifier: Apache-2.0
-Object.defineProperty(exports, "__esModule", { value: true });
-exports.AwsCrc32 = void 0;
-var tslib_1 = require("tslib");
-var util_1 = require("@aws-crypto/util");
-var index_1 = require("./index");
-var AwsCrc32 = /** @class */ (function () {
-    function AwsCrc32() {
-        this.crc32 = new index_1.Crc32();
-    }
-    AwsCrc32.prototype.update = function (toHash) {
-        if ((0, util_1.isEmptyData)(toHash))
-            return;
-        this.crc32.update((0, util_1.convertToBuffer)(toHash));
-    };
-    AwsCrc32.prototype.digest = function () {
-        return tslib_1.__awaiter(this, void 0, void 0, function () {
-            return tslib_1.__generator(this, function (_a) {
-                return [2 /*return*/, (0, util_1.numToUint8)(this.crc32.digest())];
-            });
-        });
-    };
-    AwsCrc32.prototype.reset = function () {
-        this.crc32 = new index_1.Crc32();
-    };
-    return AwsCrc32;
-}());
-exports.AwsCrc32 = AwsCrc32;
-//# sourceMappingURL=aws_crc32.js.map