feat(03-02): add SkillDetail pane, SkillAgentToggles, and assignment query IPC

- Add listSkillAgents and listAgentSkills IPC channels with Zod schemas
- Create SkillDetail component with metadata, file viewer, update check, delete
- Create SkillAgentToggles with discriminated union for skill/agent-centric modes
- Wire SkillDetail into SkillsSection right column replacing placeholder
- Remove duplicate skill method declarations from DesktopApi type

src/main/ipc-domain-handlers.ts

@@ -19,5 +19,6 @@ export function registerDomainHandlers(dependencies: RegisterDomainHandlersDepen
     ensureCompanyExists: dependencies.ensureCompanyExists,
     publishDomainChanged: dependencies.publishDomainChanged,
     skillService: dependencies.skillService,
+    db: dependencies.db,
   });
 }