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/@smithy/util-stream/dist-cjs/getAwsChunkedEncodingStream.js

@@ -1,30 +0,0 @@
-"use strict";
-Object.defineProperty(exports, "__esModule", { value: true });
-exports.getAwsChunkedEncodingStream = void 0;
-const stream_1 = require("stream");
-const getAwsChunkedEncodingStream = (readableStream, options) => {
-    const { base64Encoder, bodyLengthChecker, checksumAlgorithmFn, checksumLocationName, streamHasher } = options;
-    const checksumRequired = base64Encoder !== undefined &&
-        checksumAlgorithmFn !== undefined &&
-        checksumLocationName !== undefined &&
-        streamHasher !== undefined;
-    const digest = checksumRequired ? streamHasher(checksumAlgorithmFn, readableStream) : undefined;
-    const awsChunkedEncodingStream = new stream_1.Readable({ read: () => { } });
-    readableStream.on("data", (data) => {
-        const length = bodyLengthChecker(data) || 0;
-        awsChunkedEncodingStream.push(`${length.toString(16)}\r\n`);
-        awsChunkedEncodingStream.push(data);
-        awsChunkedEncodingStream.push("\r\n");
-    });
-    readableStream.on("end", async () => {
-        awsChunkedEncodingStream.push(`0\r\n`);
-        if (checksumRequired) {
-            const checksum = base64Encoder(await digest);
-            awsChunkedEncodingStream.push(`${checksumLocationName}:${checksum}\r\n`);
-            awsChunkedEncodingStream.push(`\r\n`);
-        }
-        awsChunkedEncodingStream.push(null);
-    });
-    return awsChunkedEncodingStream;
-};
-exports.getAwsChunkedEncodingStream = getAwsChunkedEncodingStream;