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/lib/notifications/notifications.test.ts

@@ -232,6 +232,53 @@ describe("notifications", () => {
       // Should not throw
       await expect(soundPlayer.play(NotificationType.SUCCESS)).resolves.toBeUndefined();
     });
+
+    it("play warns when audio type is not in the cache", async () => {
+      const { soundPlayer } = await import("./soundPlayer");
+      const warnSpy = vi.spyOn(console, "warn").mockImplementation(() => {});
+
+      soundPlayer.setEnabled(true);
+      await soundPlayer.play("nonexistent" as NotificationType);
+
+      expect(warnSpy).toHaveBeenCalledWith("No audio found for notification type: nonexistent");
+      warnSpy.mockRestore();
+    });
+
+    it("play catches errors from audio playback", async () => {
+      vi.resetModules();
+
+      class FailingAudio {
+        volume = 1;
+        preload = "auto";
+
+        cloneNode() {
+          const clone = new FailingAudio();
+          clone.volume = this.volume;
+          return clone;
+        }
+
+        async play(): Promise<void> {
+          throw new Error("Playback blocked by browser");
+        }
+      }
+
+      const originalAudio = globalThis.Audio;
+      globalThis.Audio = FailingAudio as unknown as typeof Audio;
+
+      const { soundPlayer: freshPlayer } = await import("./soundPlayer");
+      const errorSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+
+      freshPlayer.setEnabled(true);
+      await freshPlayer.play(NotificationType.SUCCESS);
+
+      expect(errorSpy).toHaveBeenCalledWith(
+        "Failed to play notification sound:",
+        expect.any(Error)
+      );
+
+      errorSpy.mockRestore();
+      globalThis.Audio = originalAudio;
+    });
   });
 
   describe("NotificationManager class", () => {