Variable RequestPhaseNameConst

Stage a request has reached, in the order a turn passes through them.

The reader waits through the setup stages before the first token arrives, and that wait is dominated by whichever one is slow for their setup (a cold MCP server, a summarization pass over a long feed), so each is named rather than folded into a single "working" state. The stages past setup (generating, calling-tool) keep the line alive for the rest of the turn: an agentic turn spends most of its time in tool calls, where a cleared line reads as a finished request.