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/browser/tsconfig.json

@@ -9,17 +9,15 @@
     "types": [
       "../../node_modules/@types/mocha"
     ],
-    "skipLibCheck": true,
-    "paths": {
-      "common/*": [ "./../common/*" ],
-      "*": [ "./../*" ]
-    }
+    "skipLibCheck": true
   },
   "include": [
     "./**/*",
     "../../typings/xterm.d.ts"
   ],
   "references": [
-    { "path": "../common" }
+    {
+      "path": "../common"
+    }
   ]
 }