feat: another wave of features (#61)

## Explanation

This PR bundles several user-facing improvements and feature additions for the v0.3.0 release, including quality-of-life improvements to the UI, new slash commands, better state persistence, and auto-update checking.

## Included Changes

- **Resizable chat input** with drag handle (#58 partial)
- **Arrow key navigation fix** - cursor keys now navigate text when user has typed input (#58)
- **Scroll position persistence** per conversation tab
- **/skill command** for invoking Claude Code skills (#57)
- **Stats persistence fix** - stats now persist across session changes, only reset on disconnect (#59)
- **Auto-update checker** on startup (#17)
- **Resizable character panel** with full-height sprites (#10)
- **Font size and zoom settings** with keyboard shortcuts (Ctrl++/Ctrl+-/Ctrl+0) (#19)

## Closes

Closes #10, #17, #19, #57, #58, #59

## Attestations

- [x] I have read and agree to the Code of Conduct
- [x] I have read and agree to the Community Guidelines
- [x] My contribution complies with the Contributor Covenant
- [x] I have run the linter and resolved any errors
- [x] My pull request uses an appropriate title, matching the conventional commit standards
- [x] My scope of feat/fix/chore/etc. correctly matches the nature of changes in my pull request
- [x] All new and existing tests pass locally with my changes
- [x] Code coverage remains at or above the configured threshold

## Documentation

N/A - Internal app features

## Versioning

Minor - My pull request introduces new non-breaking features.

---
✨ This PR was created with help from Hikari~ 🌸

Co-authored-by: Hikari <hikari@nhcarrigan.com>
Reviewed-on: #61
Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Co-committed-by: Naomi Carrigan <commits@nhcarrigan.com>

src/lib/commands/slashCommands.ts

@@ -183,6 +183,61 @@ 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 no skill name provided, list available skills
+      if (!skillName) {
+        try {
+          const skills = await invoke<string[]>("list_skills");
+          if (skills.length === 0) {
+            claudeStore.addLine(
+              "system",
+              "No skills found in ~/.claude/skills/\nCreate a skill by adding a folder with a SKILL.md file."
+            );
+          } else {
+            const skillList = skills.map((s) => `  • ${s}`).join("\n");
+            claudeStore.addLine(
+              "system",
+              `Available skills:\n${skillList}\n\nUsage: /skill <skill-name> [data]`
+            );
+          }
+        } catch (error) {
+          claudeStore.addLine("error", `Failed to list skills: ${error}`);
+        }
+        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): {