Show reasoning effort per agent + id copy buttons

[Maksandre]

What

Reasoning effort per agent. Claude Code writes an effort field (low … max) on every assistant record. It's now normalized (NormMsg.effort → NormAgent.effort / NormSession.effort, taking the dominant value across an agent's turns, since a run can switch effort midway) and rendered as a 5-step bar meter:

• Agents view — full badge (meter + word) next to the model badge in the agent and main-agent headers; compact meter-only in the delegation tree and the delegated-work list.
• Stats — compact meter in the model column of the per-agent table (hidden at phone width, where that column has no room).
• Conversation header — full badge for the session's effort.

Traces predating the field render nothing. If subagent meta.json starts carrying effort, that value takes precedence over the derived one.

Id copy buttons. A copy conversation id button in the conversation header and the main-agent header, and copy agent id in the subagent header (replacing the truncated id a9a3816519 text). The ids themselves stay hidden — they're only useful pasted elsewhere. Shared CopyIdButton + lib/clipboard.ts, the latter also replacing a duplicate copyText that lived in StatsView.

Verified

• tsc clean; 21 tests pass (three trace fixtures updated for the two new NormSession fields).
• Driven in a real browser against a live session: badges render in both themes, and clicking the buttons puts the session uuid / full agent id on the clipboard with a "✓ copied" confirmation.

🤖 Generated with Claude Code