Discoverable context menu for disabling CodeLens

[Copilot]

CodeLens has no in-UI affordance to identify or disable it — right-clicking a CodeLens currently invokes its command (often opening another file), and the only way to turn it off is the undocumented editor.codeLens setting.

Changes

• New MenuId.EditorCodeLensContext — context menu shown when right-clicking a CodeLens widget, following the StickyScrollContext pattern.
• codelensController.ts
  • Gate the lens click handler on e.event.leftButton so right-click no longer fires the lens command.
  • Add an onContextMenu handler that detects clicks inside .codelens-decoration and pops the new menu.
  • Register editor.action.toggleCodeLens (Action2, toggled against config.editor.codeLens), contributed to the Command Palette, View → Appearance menubar (group 4_editor, next to Sticky Scroll), and the new context menu.
  • Surface the existing codelens.showLensesInCurrentLine action in the same context menu, gated by EditorContextKeys.hasCodeLensProvider.

Notes

• The toggle flips the global editor.codeLens setting; per-provider disable is out of scope.
• Existing ContextMenuController already preventDefaults on CONTENT_WIDGET targets, so there is no native-menu conflict.