fix(agent): align agent row cards

[Ziqi XU (Ziqi418)]

Summary

• Keep agent rows constrained to the settings content column.
• Allow the agent row flex layout and last-message preview to shrink before truncating long prompts.
• Match the agent row card spacing with the adapter summary card.

Screenshots / videos

Before:

After:

Validation

• bun test apps/agent/entrypoints/app/agents/agent-row/agent-row.helpers.test.ts apps/agent/entrypoints/app/agents/agents-list-order.test.ts apps/agent/entrypoints/app/agents/useAgents.test.ts
• bunx biome check apps/agent/entrypoints/app/agents/AgentList.tsx apps/agent/entrypoints/app/agents/AgentRowCard.tsx apps/agent/entrypoints/app/agents/agent-row/AgentLastMessage.tsx
• bun run --filter @browseros/agent --elide-lines=0 build:dev

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[Ziqi XU (Ziqi418)]

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[Ziqi XU (Ziqi418)]

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