Remove TypeScript path mappings in favor of relative imports

Fixes https://github.com/xtermjs/xterm.js/issues/5896

TypeScript path mappings for common/*, browser/*, and headless/*
were not rewritten in emitted JavaScript, which forced webpack resolve
aliases and NODE_PATH workarounds so runtime could resolve modules.
That added build complexity and broke tooling such as ESLint import/no-cycle.

Changes:
- Convert ~750 imports across src/, addons/, and test/ to relative paths
- Remove common/browser/headless paths and src catch-all mappings from tsconfigs
  (keep @xterm/addon-* demo and addon typings paths)
- Remove webpack resolve.alias for common, browser, headless, and vs
- Drop NODE_PATH from unit tests, benchmarks, and VS Code launch config
- Fix addon-image IIPImageStorage to import ./Types after removing catch-all *

Verified: npm run build, esbuild, package, package-headless
Co-authored-by: Cursor <cursoragent@cursor.com>

addons/addon-progress/src/ProgressAddon.ts

@@ -5,7 +5,7 @@
 
 import type { Terminal, ITerminalAddon, IDisposable } from '@xterm/xterm';
 import type { ProgressAddon as IProgressApi, IProgressState } from '@xterm/addon-progress';
-import type { Emitter, IEvent } from 'common/Event';
+import type { Emitter, IEvent } from '../../../src/common/Event';
 
 
 const enum ProgressType {

addons/addon-progress/src/tsconfig.json

@@ -15,12 +15,6 @@
       "../../../node_modules/@types/mocha"
     ],
     "paths": {
-      "common/*": [
-        "../../../src/common/*"
-      ],
-      "browser/*": [
-        "../../../src/browser/*"
-      ],
       "@xterm/addon-progress": [
         "../typings/addon-progress.d.ts"
       ]