chore: remove dead code (59 unused files + ~125 unused exports) (#1835)

* chore: remove dead/unreferenced files across ui, vscode

Remove 59 unused source files (components, hooks, lib utils, stores,
barrels, and orphaned vscode github modules) that are not imported by
any entry-reachable code. Also drop a stale test mock for the removed
execCommands module.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* refactor: remove unused exported symbols (types, functions, consts, hooks)

Remove exported symbols whose identifier is referenced nowhere in the
repository (verified via repo-wide search), across ui types/contracts,
lib utilities, sync layer, stores, and components. Also drop the few
imports/private helpers orphaned by these removals.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* refactor: remove more unused exports (desktop, shortcuts, worktree, vscode)

Continue removing repo-wide unreferenced exported functions, consts and
types across lib/desktop, shortcuts, worktreeSessionCreator, sync, and
vscode gitService, with cascading orphaned helpers/imports cleaned up.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* chore: add dead-code cleanup tooling

* refactor: checkpoint dead-code cleanup

* refactor: remove dead-code suppressions

---------

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>
Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/components/chat/composerHighlight.ts

@@ -17,7 +17,7 @@
  * with ordinary prose (`2 * 3`, `foo_bar`).
  */
 
-export type HighlightStyle =
+type HighlightStyle =
     | 'marker'
     | 'code'
     | 'codeFence'
@@ -27,7 +27,7 @@ export type HighlightStyle =
     | 'blockquote'
     | 'listMarker';
 
-export type MentionKind = 'file' | 'agent';
+type MentionKind = 'file' | 'agent';
 
 export interface HighlightRange {
     start: number;