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/utils/stateMapper.test.ts

@@ -266,6 +266,30 @@ describe("stateMapper", () => {
       expect(mapMessageToState(message)).toBeNull();
     });
 
+    it("returns null for content_block_start with unrecognised content block type", () => {
+      const message = {
+        type: "stream_event",
+        event: {
+          type: "content_block_start",
+          index: 0,
+          content_block: { type: "input_json_delta" },
+        },
+      } as unknown as ClaudeStreamMessage;
+      expect(mapMessageToState(message)).toBeNull();
+    });
+
+    it("returns null for content_block_delta with unrecognised delta type", () => {
+      const message = {
+        type: "stream_event",
+        event: {
+          type: "content_block_delta",
+          index: 0,
+          delta: { type: "input_json_delta", partial_json: "{}" },
+        },
+      } as unknown as ClaudeStreamMessage;
+      expect(mapMessageToState(message)).toBeNull();
+    });
+
     it("returns null for result with unknown subtype", () => {
       const message = {
         type: "result",