fix: apply custom UI font to full app interface

- Set document.body.style.fontFamily directly (belt-and-suspenders
  alongside the CSS variable) to ensure the font propagates
- Use var(--ui-font-family) in .app-container so the main app area
  respects the custom font (was hardcoded, blocking inheritance)
- Rename 'Custom Font' setting to 'Custom Terminal Font' for clarity

src/lib/stores/config.test.ts

@@ -1331,23 +1331,28 @@ describe("config store", () => {
     beforeEach(() => {
       document.getElementById("hikari-custom-ui-font")?.remove();
       document.documentElement.style.removeProperty("--ui-font-family");
+      document.body.style.removeProperty("font-family");
       readFileMock.mockReset();
     });
 
-    it("removes CSS variable when both path and family are null", async () => {
+    it("removes CSS variable and body font-family when both path and family are null", async () => {
       document.documentElement.style.setProperty("--ui-font-family", "'SomeFont', sans-serif");
+      document.body.style.setProperty("font-family", "'SomeFont', sans-serif");
       await applyCustomUiFont(null, null);
       expect(document.documentElement.style.getPropertyValue("--ui-font-family")).toBe("");
+      expect(document.body.style.getPropertyValue("font-family")).toBe("");
     });
 
-    it("removes CSS variable when both path and family are empty strings", async () => {
+    it("removes CSS variable and body font-family when both path and family are empty strings", async () => {
       document.documentElement.style.setProperty("--ui-font-family", "'SomeFont', sans-serif");
+      document.body.style.setProperty("font-family", "'SomeFont', sans-serif");
       await applyCustomUiFont("", "");
       expect(document.documentElement.style.getPropertyValue("--ui-font-family")).toBe("");
+      expect(document.body.style.getPropertyValue("font-family")).toBe("");
       expect(document.getElementById("hikari-custom-ui-font")).toBeNull();
     });
 
-    it("injects @import for a CSS stylesheet URL", async () => {
+    it("injects @import for a CSS stylesheet URL and applies font to body", async () => {
       await applyCustomUiFont("https://fonts.googleapis.com/css2?family=Inter", "Inter");
       const style = document.getElementById("hikari-custom-ui-font");
       expect(style).not.toBeNull();
@@ -1357,9 +1362,10 @@ describe("config store", () => {
       expect(document.documentElement.style.getPropertyValue("--ui-font-family")).toBe(
         "'Inter', sans-serif"
       );
+      expect(document.body.style.getPropertyValue("font-family")).toBe('"Inter", sans-serif');
     });
 
-    it("injects @font-face for a direct font file URL (.woff2)", async () => {
+    it("injects @font-face for a direct font file URL (.woff2) and applies font to body", async () => {
       await applyCustomUiFont("https://example.com/fonts/Inter.woff2", "Inter");
       const style = document.getElementById("hikari-custom-ui-font");
       expect(style).not.toBeNull();
@@ -1368,15 +1374,19 @@ describe("config store", () => {
       expect(document.documentElement.style.getPropertyValue("--ui-font-family")).toBe(
         "'Inter', sans-serif"
       );
+      expect(document.body.style.getPropertyValue("font-family")).toBe('"Inter", sans-serif');
     });
 
-    it("uses HikariCustomUiFont as fallback family for direct font URLs when family is empty", async () => {
+    it("uses HikariCustomUiFont as fallback family and applies it to body", async () => {
       await applyCustomUiFont("https://example.com/fonts/Inter.woff2", "");
       const style = document.getElementById("hikari-custom-ui-font");
       expect(style?.textContent).toContain("'HikariCustomUiFont'");
+      expect(document.body.style.getPropertyValue("font-family")).toBe(
+        '"HikariCustomUiFont", sans-serif'
+      );
     });
 
-    it("reads local file and embeds as data URL", async () => {
+    it("reads local file and embeds as data URL, applies font to body", async () => {
       const fakeData = new Uint8Array([104, 101, 108, 108, 111]);
       readFileMock.mockResolvedValueOnce(fakeData);
 
@@ -1388,13 +1398,17 @@ describe("config store", () => {
       expect(document.documentElement.style.getPropertyValue("--ui-font-family")).toBe(
         "'Inter', sans-serif"
       );
+      expect(document.body.style.getPropertyValue("font-family")).toBe('"Inter", sans-serif');
     });
 
-    it("sets CSS variable when only family is provided (no path)", async () => {
+    it("sets CSS variable and body font-family when only family is provided (no path)", async () => {
       await applyCustomUiFont("", "SystemUiFont");
       expect(document.documentElement.style.getPropertyValue("--ui-font-family")).toBe(
         "'SystemUiFont', sans-serif"
       );
+      expect(document.body.style.getPropertyValue("font-family")).toBe(
+        '"SystemUiFont", sans-serif'
+      );
     });
 
     it("replaces a previously injected style element", async () => {
@@ -1415,6 +1429,7 @@ describe("config store", () => {
     beforeEach(() => {
       document.getElementById("hikari-custom-ui-font")?.remove();
       document.documentElement.style.removeProperty("--ui-font-family");
+      document.body.style.removeProperty("font-family");
       readFileMock.mockReset();
       invokeMock.mockResolvedValue(undefined);
     });
@@ -1435,13 +1450,16 @@ describe("config store", () => {
       expect(document.documentElement.style.getPropertyValue("--ui-font-family")).toBe(
         "'Inter', sans-serif"
       );
+      expect(document.body.style.getPropertyValue("font-family")).toBe('"Inter", sans-serif');
     });
 
     it("clears UI font when called with nulls", async () => {
       document.documentElement.style.setProperty("--ui-font-family", "'SomeFont', sans-serif");
+      document.body.style.setProperty("font-family", "'SomeFont', sans-serif");
       await configStore.setCustomUiFont(null, null);
 
       expect(document.documentElement.style.getPropertyValue("--ui-font-family")).toBe("");
+      expect(document.body.style.getPropertyValue("font-family")).toBe("");
       expect(invokeMock).toHaveBeenCalledWith(
         "save_config",
         expect.objectContaining({