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/stores/config.ts

@@ -15,6 +15,9 @@ export interface HikariConfig {
   notifications_enabled: boolean;
   notification_volume: number;
   always_on_top: boolean;
+  update_checks_enabled: boolean;
+  character_panel_width: number | null;
+  font_size: number;
 }
 
 const defaultConfig: HikariConfig = {
@@ -29,6 +32,9 @@ const defaultConfig: HikariConfig = {
   notifications_enabled: true,
   notification_volume: 0.7,
   always_on_top: false,
+  update_checks_enabled: true,
+  character_panel_width: null,
+  font_size: 14,
 };
 
 function createConfigStore() {
@@ -89,6 +95,33 @@ function createConfigStore() {
       applyTheme(theme);
     },
 
+    setFontSize: async (size: number) => {
+      const clampedSize = Math.max(MIN_FONT_SIZE, Math.min(MAX_FONT_SIZE, size));
+      await updateConfig({ font_size: clampedSize });
+      applyFontSize(clampedSize);
+    },
+
+    increaseFontSize: async () => {
+      let currentConfig: HikariConfig = defaultConfig;
+      config.subscribe((c) => (currentConfig = c))();
+      const newSize = Math.min(MAX_FONT_SIZE, currentConfig.font_size + 2);
+      await updateConfig({ font_size: newSize });
+      applyFontSize(newSize);
+    },
+
+    decreaseFontSize: async () => {
+      let currentConfig: HikariConfig = defaultConfig;
+      config.subscribe((c) => (currentConfig = c))();
+      const newSize = Math.max(MIN_FONT_SIZE, currentConfig.font_size - 2);
+      await updateConfig({ font_size: newSize });
+      applyFontSize(newSize);
+    },
+
+    resetFontSize: async () => {
+      await updateConfig({ font_size: DEFAULT_FONT_SIZE });
+      applyFontSize(DEFAULT_FONT_SIZE);
+    },
+
     addAutoGrantedTool: async (tool: string) => {
       let currentConfig: HikariConfig = defaultConfig;
       config.subscribe((c) => (currentConfig = c))();
@@ -119,6 +152,23 @@ export function applyTheme(theme: Theme) {
   }
 }
 
+const MIN_FONT_SIZE = 10;
+const MAX_FONT_SIZE = 24;
+const DEFAULT_FONT_SIZE = 14;
+
+export function applyFontSize(size: number) {
+  if (typeof document !== "undefined") {
+    const clampedSize = Math.max(MIN_FONT_SIZE, Math.min(MAX_FONT_SIZE, size));
+    document.documentElement.style.setProperty("--terminal-font-size", `${clampedSize}px`);
+  }
+}
+
+export function clampFontSize(size: number): number {
+  return Math.max(MIN_FONT_SIZE, Math.min(MAX_FONT_SIZE, size));
+}
+
+export { MIN_FONT_SIZE, MAX_FONT_SIZE, DEFAULT_FONT_SIZE };
+
 export const configStore = createConfigStore();
 
 export const isDarkTheme = derived(configStore.config, ($config) => $config.theme === "dark");