feat(FN-4189): lift chat input height cap and add autosize behavior

Lifts the chat input height cap and enables auto-resize as the user types, improving the chat UX in `@fusion/dashboard`. Includes test coverage for the autosize behavior and a changeset for the `@runfusion/fusion` package.

Fusion-Task-Id: FN-4189

.changeset/fn-4189-chat-entry-grows.md

@@ -0,0 +1,5 @@
+---
+"@runfusion/fusion": patch
+---
+
+Raise the dashboard chat composer autosize cap so longer drafts stay readable before scrolling.

packages/dashboard/app/components/ChatView.css

@@ -1302,8 +1302,11 @@
   font-size: 14px;
   font-family: inherit;
   line-height: 1.4;
-  max-height: 120px;
+  max-height: 320px;
   min-height: 40px;
+  /* Mobile keeps the desktop cap because the surrounding chat-input-area
+     and thread flex bounds already prevent the composer from overtaking
+     the message pane before textarea scrolling engages. */
   /* touch-action: manipulation allows tap-to-focus (so iOS doesn't
      auto-dismiss the keyboard between gesture frames) and blocks
      double-tap zoom + pan/zoom gestures. We previously tried `none`

packages/dashboard/app/components/ChatView.tsx

@@ -49,6 +49,12 @@ export interface ChatViewProps {
   experimentalFeatures?: Record<string, boolean>;
 }
 
+const CHAT_INPUT_MAX_HEIGHT_PX = 320;
+
+export function clampChatInputHeight(scrollHeight: number): number {
+  return Math.min(scrollHeight, CHAT_INPUT_MAX_HEIGHT_PX);
+}
+
 function formatRelativeTime(dateStr: string): string {
   const date = new Date(dateStr);
   const now = new Date();
@@ -1526,7 +1532,7 @@ export function ChatView({ projectId, addToast, experimentalFeatures }: ChatView
         window.requestAnimationFrame(() => {
           if (!inputRef.current) return;
           inputRef.current.style.height = "auto";
-          inputRef.current.style.height = `${Math.min(inputRef.current.scrollHeight, 120)}px`;
+          inputRef.current.style.height = `${clampChatInputHeight(inputRef.current.scrollHeight)}px`;
           inputRef.current.focus();
         });
 
@@ -1565,7 +1571,7 @@ export function ChatView({ projectId, addToast, experimentalFeatures }: ChatView
       window.requestAnimationFrame(() => {
         if (!inputRef.current) return;
         inputRef.current.style.height = "auto";
-        inputRef.current.style.height = `${Math.min(inputRef.current.scrollHeight, 120)}px`;
+        inputRef.current.style.height = `${clampChatInputHeight(inputRef.current.scrollHeight)}px`;
         inputRef.current.focus();
         inputRef.current.setSelectionRange(nextCursorPos, nextCursorPos);
       });
@@ -1725,7 +1731,7 @@ export function ChatView({ projectId, addToast, experimentalFeatures }: ChatView
     }
 
     textarea.style.height = "auto";
-    textarea.style.height = `${Math.min(textarea.scrollHeight, 120)}px`;
+    textarea.style.height = `${clampChatInputHeight(textarea.scrollHeight)}px`;
   }, [updateMentionState]);
 
   const handleInputSelectionChange = useCallback(

packages/dashboard/app/components/__tests__/ChatView.chat-input-autosize.test.tsx

@@ -0,0 +1,24 @@
+import { readFileSync } from "node:fs";
+import { resolve } from "node:path";
+import { describe, expect, it } from "vitest";
+import { clampChatInputHeight } from "../ChatView";
+
+const chatViewCss = readFileSync(resolve(__dirname, "../ChatView.css"), "utf8");
+
+describe("ChatView chat input autosize", () => {
+  it("keeps the textarea CSS max-height aligned with the raised autosize cap", () => {
+    const textareaRule = chatViewCss.match(/\.chat-input-textarea\s*\{[^}]*\}/);
+
+    expect(textareaRule).not.toBeNull();
+    expect(textareaRule?.[0]).toContain("max-height: 320px");
+  });
+
+  it("clamps oversized textarea growth to the new max height", () => {
+    expect(clampChatInputHeight(600)).toBe(320);
+    expect(clampChatInputHeight(600)).not.toBe(120);
+  });
+
+  it("preserves smaller textarea heights below the cap", () => {
+    expect(clampChatInputHeight(80)).toBe(80);
+  });
+});