Scope agent-mode thinking level

[rogerchappel]

Summary

• pass OpenClaw chat.send thinking through the CrewCMD gateway client
• send thinking: low only when the chat UI is in agent mode
• add route coverage proving agent mode scopes the thinking override

Validation

• pnpm typecheck
• pnpm vitest run src/app/api/chat/route.test.ts src/lib/gateway-reliability-harness.test.ts
• pnpm lint:check (passes with existing warnings)
• git push hook also ran pnpm typecheck and pnpm build successfully

Notes

• Leaves normal text chat behavior untouched.
• Leaves untracked docs/examples/mobile/org.mobile.local.json out of the PR.