Add oxlint import/no-cycle and break existing src/common cycles

Enable oxlint's import/no-cycle rule (import plugin) so circular module
dependencies are caught in CI, similar to eslint-plugin-import/no-cycle
and biome no-import-cycles discussed in the issue.

Relocate shared types and dependencies to remove cycles under src/common:

- Types.ts: host IInsertEvent, IDeleteEvent, IParams, UnderlineStyle,
  IBuffer, and IBufferSet; drop imports from CircularList, buffer/Types,
  parser/Types, and Services
- CoreTerminal.ts: define and export ICoreTerminal
- ServiceRegistry.ts: define IServiceIdentifier (break Services registry loop)
- UnicodeService: stop constructing UnicodeV6; CoreTerminal registers the
  default v6 provider after service creation
- buffer/Types.ts and parser/Types.ts: re-export moved types for callers

Fixes https://github.com/xtermjs/xterm.js/issues/5897

Co-authored-by: Cursor <cursoragent@cursor.com>

src/common/services/UnicodeService.test.ts

@@ -4,6 +4,7 @@
  */
 
 import { assert } from 'chai';
+import { UnicodeV6 } from '../input/UnicodeV6';
 import { UnicodeService } from './UnicodeService';
 import { IUnicodeVersionProvider } from './Services';
 
@@ -21,6 +22,7 @@ describe('unicode provider', () => {
   let us: UnicodeService;
   beforeEach(() => {
     us = new UnicodeService();
+    us.register(new UnicodeV6());
   });
   it('default to V6', () => {
     assert.equal(us.activeVersion, '6');