Describe what compaction options do to the conversation

Summarize and drop named the mechanism but not the tradeoff: an
operator had no way to know summarize spends a model call while
drop is free, or that drop also strips tool output from every turn
it keeps, not only the ones it discards. The setting row now states
the cost difference, that behaviour, and which mode is the default.

Author: TheGreatAxios

src/tui-opentui/command-surfaces.ts

@@ -289,7 +289,8 @@ function settingsCycleRows(
       describe: {
         what: "how the transcript is trimmed once the context fills.",
         impact:
-          "summarize spends a model call and keeps the thread; drop is instant and loses the middle of the session.",
+          "summarize (default) spends a call; drop is free but also strips tool output.",
+        tone: "consequence",
       },
       cycle: (dir) =>
         settings.setCompactionMode(