feat: add /skill command for invoking Claude Code skills

- New slash command: /skill <name> <data>
- Sends prompt to Claude to run skills from ~/.claude/skills/
- Shows usage help if skill name is missing

Closes #57

src/lib/commands/slashCommands.ts

@@ -183,6 +183,47 @@ export const slashCommands: SlashCommand[] = [
       }
     },
   },
+  {
+    name: "skill",
+    description: "Invoke a Claude Code skill from ~/.claude/skills/",
+    usage: "/skill <name> <data>",
+    execute: async (args: string) => {
+      const conversationId = get(claudeStore.activeConversationId);
+      if (!conversationId) {
+        claudeStore.addLine("error", "No active conversation");
+        return;
+      }
+
+      const parts = args.trim().split(/\s+/);
+      const skillName = parts[0];
+      const skillData = parts.slice(1).join(" ");
+
+      if (!skillName) {
+        claudeStore.addLine(
+          "error",
+          "Usage: /skill <skill-name> <data>\nExample: /skill onboard-mentee Discord ID: 123, GitHub: username"
+        );
+        return;
+      }
+
+      try {
+        claudeStore.addLine("system", `Invoking skill: ${skillName}`);
+        characterState.setState("thinking");
+
+        const message = skillData
+          ? `Please run the /${skillName} skill with the following data:\n\n${skillData}`
+          : `Please run the /${skillName} skill.`;
+
+        await invoke("send_prompt", {
+          conversationId,
+          message,
+        });
+      } catch (error) {
+        claudeStore.addLine("error", `Failed to invoke skill: ${error}`);
+        characterState.setTemporaryState("error", 3000);
+      }
+    },
+  },
 ];
 
 export function parseSlashCommand(input: string): {