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/InstantiationService.ts

@@ -9,8 +9,8 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
-import { IInstantiationService, IServiceIdentifier } from './Services';
-import { getServiceDependencies } from './ServiceRegistry';
+import { IInstantiationService } from './Services';
+import { IServiceIdentifier, getServiceDependencies } from './ServiceRegistry';
 
 export class ServiceCollection {