Add screen context to realtime voice consults

[rogerchappel]

Summary

• Attach current CrewCMD page context to realtime openclaw_agent_consult calls
• Include route, surface, selected IDs, visible IDs, document title, and a capped visible-screen text snapshot
• Preserve existing tool-call context by appending screen context instead of replacing it

Verification

• pnpm test -- src/lib/realtime-voice-gateway-relay.test.ts src/lib/realtime-voice-client.test.ts
• pnpm typecheck
• git diff --check

Risk

Medium-low. This sends a capped visible text snapshot from the current CrewCMD screen with realtime consults so voice can refer to the task or inbox item being viewed. No database or schema changes.