Colocate buffer types in buffer/Types.ts

The import/no-cycle refactor had moved IBuffer, IBufferSet, and related
cell/line types into src/common/Types.ts, with buffer/Types.ts only
re-exporting them. That inverted the natural module boundary and made
buffer code depend on the top-level types hub.

Define buffer-owned types in buffer/Types.ts instead:
- CharData, IExtendedAttrs, IAttributeData, ICellData, IBufferLine
- IMarker, IBuffer, IBufferSet, BufferIndex

Restore UnderlineStyle to buffer/Constants.ts (used by IExtendedAttrs)
and remove those definitions from Types.ts.

buffer/Types.ts imports only what it needs from outside the buffer layer:
ICircularList and ICharset from Types, IDisposable from Lifecycle,
IEvent from Event, and UnderlineStyle from Constants. Types.ts does not
import buffer/Types.ts, so the previous Types <-> buffer cycle stays broken.

Update imports across common, browser, headless, addons, and tests to use
common/buffer/Types for buffer types rather than common/Types.

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

src/browser/services/SelectionService.ts

@@ -11,10 +11,10 @@ import { ISelectionRedrawRequestEvent, ISelectionRequestScrollLinesEvent } from
 import { ICoreBrowserService, IMouseCoordsService, IRenderService, ISelectionService } from './Services';
 import { Disposable, MutableDisposable, toDisposable } from '../../common/Lifecycle';
 import * as Browser from '../../common/Platform';
-import { IBufferLine, ICellData, IDisposable } from '../../common/Types';
+import { IDisposable } from '../../common/Types';
+import { IBuffer, IBufferLine, ICellData } from '../../common/buffer/Types';
 import { getRangeLength } from '../../common/buffer/BufferRange';
 import { CellData } from '../../common/buffer/CellData';
-import { IBuffer } from '../../common/buffer/Types';
 import { IBufferService, ICoreService, IMouseStateService, IOptionsService } from '../../common/services/Services';
 import { Emitter } from '../../common/Event';