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-webgl/src/CharAtlasCache.ts

@@ -5,10 +5,10 @@
 
 import { TextureAtlas } from './TextureAtlas';
 import { ITerminalOptions, Terminal } from '@xterm/xterm';
-import { ITerminal, ReadonlyColorSet } from 'browser/Types';
+import { ITerminal, ReadonlyColorSet } from '../../../src/browser/Types';
 import { ICharAtlasConfig, ITextureAtlas } from './Types';
 import { generateConfig, configEquals } from './CharAtlasUtils';
-import type { ILogService } from 'common/services/Services';
+import type { ILogService } from '../../../src/common/services/Services';
 
 interface ITextureAtlasCacheEntry {
   atlas: ITextureAtlas;