feat: multiple UI improvements, font settings, and memory file display names (#175)

## Summary

- **fix**: `show_thinking_blocks` setting now persists across sessions — it was defined on the TypeScript side but missing from the Rust `HikariConfig` struct, so serde silently dropped it on every save/load
- **feat**: Tool calls are now rendered as collapsible blocks matching the Extended Thinking block aesthetic, replacing the old inline dropdown approach
- **feat**: Add configurable max output tokens setting
- **feat**: Use random creative names for conversation tabs
- **test**: Significantly expanded frontend unit test coverage
- **docs**: Require tests for all changes in CLAUDE.md
- **feat**: Allow users to specify a custom terminal font (Closes #176)
- **feat**: Display friendly names for memory files derived from the first heading (Closes #177)
- **feat**: Add custom UI font support for the app chrome (buttons, labels, tabs)
- **fix**: Apply custom UI font to the full app interface — `.app-container` was hardcoded, blocking inheritance from `body`; also renamed "Custom Font" to "Custom Terminal Font" for clarity

✨ This PR was created with help from Hikari~ 🌸

Reviewed-on: #175
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

src/routes/+page.svelte

@@ -11,7 +11,14 @@
     updateDiscordRpc,
     setSkipNextGreeting,
   } from "$lib/tauri";
-  import { configStore, applyTheme, applyFontSize, isCompactMode } from "$lib/stores/config";
+  import {
+    configStore,
+    applyTheme,
+    applyFontSize,
+    applyCustomFont,
+    applyCustomUiFont,
+    isCompactMode,
+  } from "$lib/stores/config";
   import { readFile } from "@tauri-apps/plugin-fs";
   import { initNotificationSync, cleanupNotificationSync } from "$lib/stores/notifications";
   import { conversationsStore } from "$lib/stores/conversations";
@@ -454,6 +461,8 @@
       const config = configStore.getConfig();
       applyTheme(config.theme, config.custom_theme_colors);
       applyFontSize(config.font_size);
+      await applyCustomFont(config.custom_font_path, config.custom_font_family);
+      await applyCustomUiFont(config.custom_ui_font_path, config.custom_ui_font_family);
 
       // Apply always-on-top setting
       if (config.always_on_top) {
@@ -593,13 +602,15 @@
 
 <style>
   .app-container {
-    font-family:
+    font-family: var(
+      --ui-font-family,
       "Inter",
       -apple-system,
       BlinkMacSystemFont,
       "Segoe UI",
       Roboto,
-      sans-serif;
+      sans-serif
+    );
   }
 
   .character-panel {