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/uuid/dist-cjs/index.js

@@ -1,36 +0,0 @@
-'use strict';
-
-var randomUUID = require('./randomUUID');
-
-const decimalToHex = Array.from({ length: 256 }, (_, i) => i.toString(16).padStart(2, "0"));
-const v4 = () => {
-    if (randomUUID.randomUUID) {
-        return randomUUID.randomUUID();
-    }
-    const rnds = new Uint8Array(16);
-    crypto.getRandomValues(rnds);
-    rnds[6] = (rnds[6] & 0x0f) | 0x40;
-    rnds[8] = (rnds[8] & 0x3f) | 0x80;
-    return (decimalToHex[rnds[0]] +
-        decimalToHex[rnds[1]] +
-        decimalToHex[rnds[2]] +
-        decimalToHex[rnds[3]] +
-        "-" +
-        decimalToHex[rnds[4]] +
-        decimalToHex[rnds[5]] +
-        "-" +
-        decimalToHex[rnds[6]] +
-        decimalToHex[rnds[7]] +
-        "-" +
-        decimalToHex[rnds[8]] +
-        decimalToHex[rnds[9]] +
-        "-" +
-        decimalToHex[rnds[10]] +
-        decimalToHex[rnds[11]] +
-        decimalToHex[rnds[12]] +
-        decimalToHex[rnds[13]] +
-        decimalToHex[rnds[14]] +
-        decimalToHex[rnds[15]]);
-};
-
-exports.v4 = v4;