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>

src/common/Types.ts

@@ -3,13 +3,13 @@
  * @license MIT
  */
 
-import { IDeleteEvent, IInsertEvent } from 'common/CircularList';
-import { UnderlineStyle } from 'common/buffer/Constants';
-import { IBufferSet } from 'common/buffer/Types';
-import { IParams } from 'common/parser/Types';
-import { IMouseStateService, ICoreService, IOptionsService, IUnicodeService } from 'common/services/Services';
+import { IDeleteEvent, IInsertEvent } from './CircularList';
+import { UnderlineStyle } from './buffer/Constants';
+import { IBufferSet } from './buffer/Types';
+import { IParams } from './parser/Types';
+import { IMouseStateService, ICoreService, IOptionsService, IUnicodeService } from './services/Services';
 import { IFunctionIdentifier, ITerminalOptions as IPublicTerminalOptions } from '@xterm/xterm';
-import type { Emitter, IEvent } from 'common/Event';
+import type { Emitter, IEvent } from './Event';
 
 export interface ICoreTerminal {
   mouseStateService: IMouseStateService;