Summary

• reuse the configured model collector in the agents overview picker so provider-qualified primary, fallback, and allowlisted model refs stay selectable
• add a regression test that keeps the chat header picker sending the full provider-qualified model when switching across providers
• add coverage for the overview picker so it shows configured provider-qualified values instead of falling back to a synthetic Current (...) entry

Testing

• corepack pnpm --dir ui exec vitest run src/ui/views/chat.test.ts src/ui/views/agents.test.ts src/ui/views/agents-utils.test.ts --config vitest.config.ts
• corepack pnpm --dir ui exec vitest run src/ui/chat-model-ref.test.ts src/ui/chat/slash-command-executor.node.test.ts --config vitest.config.ts

Closes openclaw#51608
Closes openclaw#51510