Add click-to-copy workspace path on Paperclip workspace source label

When a skill's source is "Paperclip workspace", clicking the label now
copies the absolute path to the managed skills workspace to the clipboard
and shows a toast confirmation.

- Add sourcePath field to CompanySkillDetail and CompanySkillListItem types
- Return managedRoot path as sourcePath from deriveSkillSourceInfo for
  Paperclip workspace skills
- Make source label a clickable button in SkillPane detail view

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/shared/src/types/company-skill.ts

@@ -50,6 +50,7 @@ export interface CompanySkillListItem {
   editableReason: string | null;
   sourceLabel: string | null;
   sourceBadge: CompanySkillSourceBadge;
+  sourcePath: string | null;
 }
 
 export interface CompanySkillUsageAgent {
@@ -68,6 +69,7 @@ export interface CompanySkillDetail extends CompanySkill {
   editableReason: string | null;
   sourceLabel: string | null;
   sourceBadge: CompanySkillSourceBadge;
+  sourcePath: string | null;
 }
 
 export interface CompanySkillUpdateStatus {