ui: a signal's details sit directly under its name; its unit is user-changeable and saved with the session

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/claude/invariants-session-and-export.md

@@ -23,7 +23,10 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   not follow the lock). `[sigbadges] drag_sources` is the reading, and `drag_sources` on the `signals panel:`
   line must be 0.
 - **The session is the layout.** `LayoutState` persists what makes a reopened scope look like the
-  one that was closed: the window, the rows and their slot signals, the calibration, **the enabled
+  one that was closed: the window, the rows and their slot signals, the calibration, **the unit renames**
+  (`[[unit]]`, `name` + `unit`, only the overrides; `ScopeModel::set_signal_unit` re-applies them to every CONFIG,
+  and `set_signals()` takes them off the incoming units before the "same stream" comparison so a reconnect still
+  keeps its history), **the enabled
   signals**, **the chosen trace colours** (`[[color]]`, `name` + `rgb = "#RRGGBB"` — only the
   *overrides*, so a stream's new signals still take the positional palette and a saved session does
   not freeze a colour that is meant to follow the signal list), **the math channels with their