docs: the readouts dock, the cursors and measurement pages

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

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

@@ -31,7 +31,7 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   toggle; written as a bare top-level boolean (`measure_stats = true/false`), defaults to `false`
   when absent, and **`dock`** -- `LayoutState::dock_shown`, the Dock button's state (the user's last word on it,
   `App::sidebar_wanted`): a bare top-level boolean written where `side_tab` used to be, default `true`.
-  It is the **only** thing the dock persists -- its 320 px width is fixed, so there is nothing to store --
+  It is the **only** thing the dock persists -- its 280 px width is fixed, so there is nothing to store --
   and **the open slide-over page is deliberately not persisted** (a panel that opens by itself at start-up
   is a surprise, and a page id from another source kind may not exist). The parser ignores unknown keys
   (its key chain has no erroring final `else`), so a file written before the tabs became a dock