fix(mobile): bump focused-input font-size to 16px (kills iOS focus-zoom)

iOS Safari and PWAs auto-zoom the viewport when a focused input or
textarea has a computed font-size below 16px. Two mobile-canvas inputs
were below that bound, causing the layout to jump and look broken on
focus until the user pinched back:

  - MobileSpawn.tsx agent-name input (fontSize: 13.5) — #225
  - MobileChat.tsx composer textarea (fontSize: 14.5) — #224

Both bumped to 16px (the minimum that suppresses focus-zoom). This is
the same class of bug as desktop #1434, scoped here to the mobile
breakpoint.

Tests:
  - MobileSpawn.test: assert agent-name input renders at fontSize >= 16
  - MobileChat.test:  assert composer textarea renders at fontSize >= 16
Both parse the inline style.fontSize (jsdom has no layout engine, so
getComputedStyle reports the inline value verbatim).

Closes #224
Closes #225

canvas/src/components/mobile/MobileChat.tsx

@@ -756,7 +756,12 @@ export function MobileChat({
               border: "none",
               outline: "none",
               background: "transparent",
-              fontSize: 14.5,
+              // iOS Safari/PWA zooms the viewport when a focused textarea
+              // has a computed font-size below 16px. 14.5 triggers that
+              // focus-zoom; the page looks broken until the user pinches
+              // back (#224, same class as desktop #1434 / sibling #225).
+              // 16px is the minimum that keeps focus from zooming.
+              fontSize: 16,
               lineHeight: 1.4,
               color: p.text,
               padding: "6px 0",

canvas/src/components/mobile/MobileSpawn.tsx

@@ -318,7 +318,12 @@ export function MobileSpawn({ dark, onClose }: { dark: boolean; onClose: () => v
               border: `0.5px solid ${p.border}`,
               borderRadius: 12,
               fontFamily: MOBILE_FONT_MONO,
-              fontSize: 13.5,
+              // iOS Safari/PWA zooms the viewport when a focused input has
+              // a computed font-size below 16px; the layout jumps and the
+              // page looks broken until the user pinches back (#224 / #225,
+              // same class as desktop #1434). 16px is the minimum that
+              // suppresses that focus-zoom.
+              fontSize: 16,
               color: p.text,
               outline: "none",
               boxSizing: "border-box",

canvas/src/components/mobile/__tests__/MobileChat.test.tsx

@@ -263,6 +263,20 @@ describe("MobileChat — composer", () => {
     const sendBtn = container.querySelector('[aria-label="Send"]') as HTMLButtonElement;
     expect(sendBtn.disabled).toBe(true);
   });
+
+  // Regression #224: the composer textarea must render with font-size
+  // ≥ 16px. iOS Safari and PWAs auto-zoom the viewport when a focused
+  // input has a computed font-size below 16px — the layout jumps and
+  // the page looks broken until the user pinches back. Same class as
+  // desktop #1434 / sibling MobileSpawn #225.
+  it("composer textarea renders at font-size 16px or greater (iOS focus-zoom regression #224)", () => {
+    const { container } = renderChat(mockAgentId);
+    const textarea = container.querySelector("textarea") as HTMLTextAreaElement;
+    expect(textarea).toBeTruthy();
+    const fs = Number.parseFloat(textarea.style.fontSize);
+    expect(Number.isFinite(fs)).toBe(true);
+    expect(fs).toBeGreaterThanOrEqual(16);
+  });
 });
 
 // ─── Tabs ─────────────────────────────────────────────────────────────────────

canvas/src/components/mobile/__tests__/MobileSpawn.test.tsx

@@ -93,6 +93,24 @@ describe("MobileSpawn — render", () => {
     expect(input).toBeTruthy();
   });
 
+  // Regression #224 / #225: the agent-name input must render with a
+  // font-size ≥ 16px. iOS Safari and PWAs auto-zoom the viewport when a
+  // focused input has a computed font-size below 16px — the layout
+  // jumps and the page looks broken until the user pinches back.
+  it("renders the name input at font-size 16px or greater (iOS focus-zoom regression)", () => {
+    apiGetSpy.mockResolvedValue(mockTemplates);
+    render(<MobileSpawn dark={true} onClose={vi.fn()} />);
+    const input = document.querySelector(
+      'input[aria-label="Agent name"]',
+    ) as HTMLInputElement | null;
+    expect(input).toBeTruthy();
+    // Parse the inline style font-size — jsdom doesn't run a layout
+    // engine, so getComputedStyle reports the inline value verbatim.
+    const fs = Number.parseFloat(input!.style.fontSize);
+    expect(Number.isFinite(fs)).toBe(true);
+    expect(fs).toBeGreaterThanOrEqual(16);
+  });
+
   it("renders all 4 tier buttons", () => {
     apiGetSpy.mockResolvedValue(mockTemplates);
     render(<MobileSpawn dark={true} onClose={vi.fn()} />);