fix: pre-landing and adversarial review fixes

- landing.css: hardcode --lp-btn to #60a5fa (lesson 104 — no var(--color-*) in landing.css)
- ScriptBuilderInput: suggestion chips now correctly disabled during generation
- ChatSidebar: wrapper onClick no longer fires onSelect while in confirming state
- SessionHistoryPage: fix loadMoreAiSessions race condition with generation counter;
  flow session tab auto-activates when URL params target flow session filters

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/script-builder/ScriptBuilderInput.tsx

@@ -92,8 +92,9 @@ export function ScriptBuilderInput({
             <button
               key={label}
               type="button"
-              onClick={() => onSend(label)}
-              className="group flex items-center gap-1.5 rounded-md border border-border bg-card px-3 py-1.5 text-xs text-muted-foreground transition-all hover:border-[var(--color-border-hover)] hover:bg-[var(--color-bg-elevated)] hover:text-foreground active:scale-[0.97]"
+              disabled={disabled}
+              onClick={() => { if (!disabled) onSend(label) }}
+              className="group flex items-center gap-1.5 rounded-md border border-border bg-card px-3 py-1.5 text-xs text-muted-foreground transition-all hover:border-[var(--color-border-hover)] hover:bg-[var(--color-bg-elevated)] hover:text-foreground active:scale-[0.97] disabled:opacity-50 disabled:cursor-not-allowed disabled:pointer-events-none"
             >
               <Icon size={11} className="text-muted shrink-0 group-hover:text-[#f97316] transition-colors" />
               {label}