Restructure common into layered folders (issue #5963)

Reorganize src/common into platform (base, encoding, data, buffer,
parser, input), integration (services, terminal), and public API layers.

- Move core utilities to common/base/
- Move TextDecoder to common/encoding/
- Move Types, CircularList, Color, TaskQueue, SortedList to common/services/
- Move CoreTerminal, InputHandler, WindowsMode to common/terminal/
- Define ICharset in common/data/Charsets.ts (re-exported from Types)
- Update imports across src/, addons/, and test/
- Add per-layer tsconfig.json files and REARCHITECTURE.md
- Root common/tsconfig.json remains the composite build entry

Co-authored-by: Daniel Imms <Tyriar@users.noreply.github.com>

src/browser/renderer/dom/DomRenderer.ts

@@ -12,10 +12,10 @@ import { TextBlinkStateManager } from 'browser/renderer/shared/TextBlinkStateMan
 import { IRenderDimensions, IRenderer, IRequestRedrawEvent, ISelectionRenderModel } from 'browser/renderer/shared/Types';
 import { ICharSizeService, ICoreBrowserService, IThemeService } from 'browser/services/Services';
 import { ILinkifier2, ILinkifierEvent, ITerminal, ReadonlyColorSet } from 'browser/Types';
-import { color } from 'common/Color';
-import { Disposable, toDisposable } from 'common/Lifecycle';
+import { color } from 'common/services/Color';
+import { Disposable, toDisposable } from 'common/base/Lifecycle';
 import { IBufferService, ICoreService, IInstantiationService, IOptionsService } from 'common/services/Services';
-import { Emitter } from 'common/Event';
+import { Emitter } from 'common/base/Event';
 import { addDisposableListener } from 'browser/Dom';
 
 

src/browser/renderer/dom/DomRendererRowFactory.test.ts

@@ -9,9 +9,9 @@ import { DomRendererRowFactory } from 'browser/renderer/dom/DomRendererRowFactor
 import { NULL_CELL_CODE, NULL_CELL_WIDTH, NULL_CELL_CHAR, DEFAULT_ATTR, FgFlags, BgFlags, Attributes, UnderlineStyle } from 'common/buffer/Constants';
 import { BufferLine, DEFAULT_ATTR_DATA } from 'common/buffer/BufferLine';
 import { BufferLineStringCache } from 'common/buffer/BufferLineStringCache';
-import { IBufferLine } from 'common/Types';
+import { IBufferLine } from 'common/services/Types';
 import { CellData } from 'common/buffer/CellData';
-import { MockCoreService, MockDecorationService, MockOptionsService, createCellData, NULL_CELL_DATA } from 'common/TestUtils.test';
+import { MockCoreService, MockDecorationService, MockOptionsService, createCellData, NULL_CELL_DATA } from 'common/terminal/TestUtils.test';
 import { MockCharacterJoinerService, MockCoreBrowserService, MockThemeService } from 'browser/TestUtils.test';
 import { TestWidthCache } from 'browser/renderer/dom/WidthCache.test';
 

src/browser/renderer/dom/DomRendererRowFactory.ts

@@ -3,12 +3,12 @@
  * @license MIT
  */
 
-import { IBufferLine, ICellData, IColor } from 'common/Types';
+import { IBufferLine, ICellData, IColor } from 'common/services/Types';
 import { INVERTED_DEFAULT_COLOR } from 'browser/renderer/shared/Constants';
 import { WHITESPACE_CELL_CHAR, Attributes } from 'common/buffer/Constants';
 import { CellData } from 'common/buffer/CellData';
 import { ICoreService, IDecorationService, IOptionsService } from 'common/services/Services';
-import { channels, color } from 'common/Color';
+import { channels, color } from 'common/services/Color';
 import { ICharacterJoinerService, ICoreBrowserService, IThemeService } from 'browser/services/Services';
 import { JoinedCellData } from 'browser/services/CharacterJoinerService';
 import { treatGlyphAsBackgroundColor } from 'browser/renderer/shared/RendererUtils';

src/browser/renderer/dom/WidthCache.ts

@@ -4,7 +4,7 @@
  */
 
 import { throwIfFalsy } from 'browser/renderer/shared/RendererUtils';
-import { IDisposable } from 'common/Types';
+import { IDisposable } from 'common/services/Types';
 import { FontWeight } from 'common/services/Services';
 
 

src/browser/renderer/shared/TextBlinkStateManager.test.ts

@@ -5,9 +5,9 @@
 
 import { assert } from 'chai';
 import { TextBlinkStateManager } from 'browser/renderer/shared/TextBlinkStateManager';
-import { MockOptionsService } from 'common/TestUtils.test';
+import { MockOptionsService } from 'common/terminal/TestUtils.test';
 import type { ICoreBrowserService } from 'browser/services/Services';
-import { Emitter } from 'common/Event';
+import { Emitter } from 'common/base/Event';
 
 class FakeWindow {
   public nextId = 1;

src/browser/renderer/shared/TextBlinkStateManager.ts

@@ -4,7 +4,7 @@
  */
 
 import { ICoreBrowserService } from 'browser/services/Services';
-import { Disposable, toDisposable } from 'common/Lifecycle';
+import { Disposable, toDisposable } from 'common/base/Lifecycle';
 import { IOptionsService } from 'common/services/Services';
 
 export class TextBlinkStateManager extends Disposable {

src/browser/renderer/shared/Types.ts

@@ -5,8 +5,8 @@
 
 import { Terminal } from '@xterm/xterm';
 import { ITerminal } from 'browser/Types';
-import { IDisposable } from 'common/Types';
-import type { IEvent } from 'common/Event';
+import { IDisposable } from 'common/services/Types';
+import type { IEvent } from 'common/base/Event';
 
 export interface IDimensions {
   width: number;