feat(web): collapse tool activity into one line - #7152

💭 This diff is mostly React UI code, so I'm checking whether any Effect library usage is involved, particularly around session-logic.ts and MessagesTimeline.logic.ts which might use Equal for comparisons. I want to verify how Equal is imported there. No Effect service definitions are touched here—this PR is pure UI logic, so there are no service convention violations. I'm confident everything is clear, though I need to reconcile the instruction to output plain text with the schema requiring JSON, so I'll follow the schema while keeping the summary minimal.