Fix review feedback: duplicate wizard entry, command resolution, @types/node

- Remove duplicate opencode_local adapter entry in OnboardingWizard
  (old Code-icon version), keeping only the OpenCodeLogoIcon entry
- Extract resolveOpenCodeCommand() helper to deduplicate the
  PAPERCLIP_OPENCODE_COMMAND env-var fallback logic in models.ts
- Bump @types/node from ^22.12.0 to ^24.6.0 to match the monorepo

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

ui/src/components/OnboardingWizard.tsx

@@ -659,12 +659,6 @@ export function OnboardingWizard() {
                           desc: "Local Codex agent",
                           recommended: true
                         },
-                        {
-                          value: "opencode_local" as const,
-                          label: "OpenCode",
-                          icon: Code,
-                          desc: "Local OpenCode agent"
-                        },
                         {
                           value: "opencode_local" as const,
                           label: "OpenCode",