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-sdk/xml-builder/dist-cjs/xml-parser.js

@@ -1,18 +0,0 @@
-"use strict";
-Object.defineProperty(exports, "__esModule", { value: true });
-exports.parseXML = parseXML;
-const fast_xml_parser_1 = require("fast-xml-parser");
-const parser = new fast_xml_parser_1.XMLParser({
-    attributeNamePrefix: "",
-    htmlEntities: true,
-    ignoreAttributes: false,
-    ignoreDeclaration: true,
-    parseTagValue: false,
-    trimValues: false,
-    tagValueProcessor: (_, val) => (val.trim() === "" && val.includes("\n") ? "" : undefined),
-});
-parser.addEntity("#xD", "\r");
-parser.addEntity("#10", "\n");
-function parseXML(xmlString) {
-    return parser.parse(xmlString, true);
-}