feat(03-01): add SkillsSection layout, SkillList, SkillFileTree, and SkillImportModal

- Create SkillsSection with two-column grid layout (19rem + flex) matching Paperclip pattern
- Create SkillList with source icons, expandable file trees, CSS grid animation
- Create SkillFileTree with recursive rendering, dir/file icons, indent levels
- Create SkillImportModal with 4 tabs: GitHub, Local Path, HTTP URL, skills.sh
- Wire listSkills IPC for skill loading and importSkill IPC for import flow
- Add skill IPC channels, Zod schemas, and DesktopApi methods to contracts.ts
- Add skill IPC bridge methods to preload/index.ts
- All Phosphor icons, all ui.tsx components, no external dependencies

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/shared/contracts.ts

@@ -1,5 +1,5 @@
 import { z } from "zod";
-import type { AgentMessageRecord, AgentMetrics, BrowserActionRecord, CommentRecord, CompanyMetrics, DesktopEvent, InboxItem, OnboardingBootstrapResult, ProfileSnapshot, RunLogChunk, StandupReport } from "./types";
+import type { AgentMessageRecord, AgentMetrics, BrowserActionRecord, CommentRecord, CompanyMetrics, DesktopEvent, InboxItem, OnboardingBootstrapResult, ProfileSnapshot, RunLogChunk, SkillImportResult, SkillRecord, SkillUpdateStatus, StandupReport } from "./types";
 
 export const IPC_CHANNELS = {
   loadSnapshot: "agent-company:load-snapshot",
@@ -73,6 +73,13 @@ export const IPC_CHANNELS = {
   runWorkflow: "agent-company:run-workflow",
   autoAssignTask: "agent-company:auto-assign-task",
   searchMessages: "agent-company:search-messages",
+  importSkill: "agent-company:import-skill",
+  listSkills: "agent-company:list-skills",
+  getSkillDetail: "agent-company:get-skill-detail",
+  deleteSkill: "agent-company:delete-skill",
+  assignSkillToAgent: "agent-company:assign-skill-to-agent",
+  removeSkillFromAgent: "agent-company:remove-skill-from-agent",
+  checkSkillUpdate: "agent-company:check-skill-update",
 } as const;
 
 const optionalId = z.preprocess(
@@ -514,6 +521,42 @@ export const autoAssignSchema = z.object({
   companyId: z.string().uuid(),
 });
 
+export const importSkillSchema = z.object({
+  companyId: z.string().uuid(),
+  source: z.string().min(1),
+});
+
+export const listSkillsSchema = z.object({
+  companyId: z.string().uuid(),
+});
+
+export const getSkillDetailSchema = z.object({
+  companyId: z.string().uuid(),
+  skillId: z.string().uuid(),
+});
+
+export const deleteSkillSchema = z.object({
+  companyId: z.string().uuid(),
+  skillId: z.string().uuid(),
+});
+
+export const assignSkillToAgentSchema = z.object({
+  companyId: z.string().uuid(),
+  agentId: z.string().uuid(),
+  skillId: z.string().uuid(),
+});
+
+export const removeSkillFromAgentSchema = z.object({
+  companyId: z.string().uuid(),
+  agentId: z.string().uuid(),
+  skillId: z.string().uuid(),
+});
+
+export const checkSkillUpdateSchema = z.object({
+  companyId: z.string().uuid(),
+  skillId: z.string().uuid(),
+});
+
 export type DesktopResult<T> =
   | { ok: true; data: T }
   | { ok: false; error: { code: string; message: string } };
@@ -592,5 +635,12 @@ export type DesktopApi = {
   recoveryRetry: (taskId: string, agentId: string, companyId: string) => Promise<DesktopResult<null>>;
   recoveryDismiss: (taskId: string) => Promise<DesktopResult<null>>;
   recoveryFail: (taskId: string) => Promise<DesktopResult<null>>;
+  importSkill: (companyId: string, source: string) => Promise<DesktopResult<SkillImportResult[]>>;
+  listSkills: (companyId: string) => Promise<DesktopResult<SkillRecord[]>>;
+  getSkillDetail: (companyId: string, skillId: string) => Promise<DesktopResult<SkillRecord>>;
+  deleteSkill: (companyId: string, skillId: string) => Promise<DesktopResult<void>>;
+  assignSkillToAgent: (companyId: string, agentId: string, skillId: string) => Promise<DesktopResult<void>>;
+  removeSkillFromAgent: (companyId: string, agentId: string, skillId: string) => Promise<DesktopResult<void>>;
+  checkSkillUpdate: (companyId: string, skillId: string) => Promise<DesktopResult<SkillUpdateStatus>>;
   subscribe: (callback: (event: DesktopEvent) => void) => () => void;
 };