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,
   });
 }

src/main/ipc-skill-handlers.ts

@@ -7,15 +7,19 @@ import {
   assignSkillToAgentSchema,
   removeSkillFromAgentSchema,
   checkSkillUpdateSchema,
+  listSkillAgentsSchema,
+  listAgentSkillsSchema,
 } from "@shared/contracts";
 import { fail, ok, type RegisterDomainHandlersDependencies } from "./ipc-domain-common";
 import type { createSkillService } from "./skill-service";
+import type { AppDatabase } from "./database";
 
 interface SkillHandlerDependencies extends Pick<
   RegisterDomainHandlersDependencies,
   "registerHandle" | "ensureCompanyExists" | "publishDomainChanged"
 > {
   skillService: ReturnType<typeof createSkillService> | null;
+  db: AppDatabase;
 }
 
 export function registerSkillHandlers({
@@ -23,6 +27,7 @@ export function registerSkillHandlers({
   ensureCompanyExists,
   publishDomainChanged,
   skillService,
+  db,
 }: SkillHandlerDependencies) {
   function requireSkillService() {
     if (!skillService) {
@@ -116,4 +121,20 @@ export function registerSkillHandlers({
     if (serviceError) return serviceError;
     return skillService!.checkUpdateStatus(parsed.companyId, parsed.skillId);
   });
+
+  // ---- List agent IDs assigned to a skill ----
+  registerHandle(IPC_CHANNELS.listSkillAgents, async (_event, payload) => {
+    const parsed = listSkillAgentsSchema.parse(payload);
+    const companyError = ensureCompanyExists(parsed.companyId);
+    if (companyError) return companyError;
+    return ok(db.listSkillAgentAssignments(parsed.skillId));
+  });
+
+  // ---- List skill IDs assigned to an agent ----
+  registerHandle(IPC_CHANNELS.listAgentSkills, async (_event, payload) => {
+    const parsed = listAgentSkillsSchema.parse(payload);
+    const companyError = ensureCompanyExists(parsed.companyId);
+    if (companyError) return companyError;
+    return ok(db.listAgentSkillAssignments(parsed.agentId));
+  });
 }