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/public/BufferNamespaceApi.ts

@@ -5,7 +5,7 @@
 
 import { IBuffer as IBufferApi, IBufferNamespace as IBufferNamespaceApi } from '@xterm/xterm';
 import { BufferApiView } from './BufferApiView';
-import { ICoreTerminal } from '../Types';
+import { ICoreTerminal } from '../CoreTerminal';
 import { Disposable } from '../Lifecycle';
 import { Emitter } from '../Event';
 

src/common/public/ParserApi.ts

@@ -5,7 +5,7 @@
 
 import { IParams } from '../parser/Types';
 import { IDisposable, IFunctionIdentifier, IParser } from '@xterm/xterm';
-import { ICoreTerminal } from '../Types';
+import { ICoreTerminal } from '../CoreTerminal';
 
 export class ParserApi implements IParser {
   constructor(private _core: ICoreTerminal) { }

src/common/public/UnicodeApi.ts

@@ -3,7 +3,7 @@
  * @license MIT
  */
 
-import { ICoreTerminal } from '../Types';
+import { ICoreTerminal } from '../CoreTerminal';
 import { IUnicodeHandling, IUnicodeVersionProvider } from '@xterm/xterm';
 
 export class UnicodeApi implements IUnicodeHandling {