[tianxiaochannel-oss88]

Summary

• Fold adjacent successful read/grep/find/ls actions into expandable activity summaries.
• Preserve atomic rows, action IDs, source references, and Continuity v2 boundaries.
• Contain activity streams with a fixed-height scroll region when more than 10 atomic rows are present; no hard truncation or virtualization.

Verification

• conversation-ui-core: 33/33 tests passed
• Web typecheck: passed
• i18n check: passed
• WorkCell activity Playwright: 8/8 passed
• git diff --check: passed

UI coverage

• Normal conversation, channel multi-agent, teammate conversation, command batch expansion, exploration batch expansion, dense 11-row scrolling, details loading/retry, reduced motion, and containment.

Test plan

• Existing activity WorkCell flows
• 11-row dense activity stream
• Expanded rows remain available
• No runtime errors or horizontal overflow