docs: add security disclaimer and improve README structure

Created comprehensive DISCLAIMER.md with security warnings about AI tooling risks and sandboxing recommendations. Updated README.md with project overview, security disclaimer section, and complete features list with emojis. Also improved git-diff-panel layout with better scrolling behavior.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4 <noreply@anthropic.com>

app/src/components/views/agent-output-modal.tsx

@@ -301,14 +301,14 @@ export function AgentOutputModal({
         </DialogHeader>
 
         {viewMode === "changes" ? (
-          <div className="flex-1 overflow-y-auto min-h-[400px] max-h-[60vh] scrollbar-visible">
+          <div className="flex-1 min-h-[400px] max-h-[60vh] overflow-hidden">
             {projectPath ? (
               <GitDiffPanel
                 projectPath={projectPath}
                 featureId={featureId}
                 compact={false}
                 useWorktrees={useWorktrees}
-                className="border-0 rounded-lg"
+                className="border-0 rounded-lg h-full"
               />
             ) : (
               <div className="flex items-center justify-center h-full text-muted-foreground">