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/eventsource-parser/dist/stream.js

@@ -1,29 +0,0 @@
-import { createParser } from "./index.js";
-import { ParseError } from "./index.js";
-class EventSourceParserStream extends TransformStream {
-  constructor({ onError, onRetry, onComment } = {}) {
-    let parser;
-    super({
-      start(controller) {
-        parser = createParser({
-          onEvent: (event) => {
-            controller.enqueue(event);
-          },
-          onError(error) {
-            onError === "terminate" ? controller.error(error) : typeof onError == "function" && onError(error);
-          },
-          onRetry,
-          onComment
-        });
-      },
-      transform(chunk) {
-        parser.feed(chunk);
-      }
-    });
-  }
-}
-export {
-  EventSourceParserStream,
-  ParseError
-};
-//# sourceMappingURL=stream.js.map