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/querystring-parser/dist-cjs/index.js

@@ -1,27 +0,0 @@
-'use strict';
-
-function parseQueryString(querystring) {
-    const query = {};
-    querystring = querystring.replace(/^\?/, "");
-    if (querystring) {
-        for (const pair of querystring.split("&")) {
-            let [key, value = null] = pair.split("=");
-            key = decodeURIComponent(key);
-            if (value) {
-                value = decodeURIComponent(value);
-            }
-            if (!(key in query)) {
-                query[key] = value;
-            }
-            else if (Array.isArray(query[key])) {
-                query[key].push(value);
-            }
-            else {
-                query[key] = [query[key], value];
-            }
-        }
-    }
-    return query;
-}
-
-exports.parseQueryString = parseQueryString;