Add Agents Window taskbar shortcut and icons - #335333

PR classified as team-member.

✅ Head commit ce3435d is signed by dmitrivMS with trusted key SHA256:SITOqsmcNrt9VCbafBaUD04K2PIPpa5sRlCjvqJMjSo — approval requirement reduced from 2 to 1.

✅ Collaborator approvals: 1/1 (rzhao271).

✅ No newly added runnable binary files.

✅ Engineering system changes are allowed.

• build/gulpfile.vscode.ts

The PR author is a current VS Code team member.