Docs: build hash grammar, theme rollback, reference-identity change detection, option-list boundary rule

docs/architecture/10-interaction-and-feedback.md

@@ -445,7 +445,14 @@ refocuses the trigger; outside press closes; open lands focus on the selected op
 Arrow/Home/End rove). The selected option carries `aria-current` and a visible ✓, never
 colour alone. The same control doubles as an **action picker** (no `value`; e.g. "Add field
 to which channel?"). A custom `triggerClassName` _replaces_ the default trigger styling, so
-chip-styled triggers (the pill's type chip, the shelf's field chips) stay chips.
+chip-styled triggers (the pill's type chip, the shelf's field chips) stay chips; the default
+trigger sits on the **32px compact control scale** (arch 09 §6), like the sort trigger and
+search input it shares surfaces with. A long option list can carry **group separators**: an
+option's `dividerBefore` draws a `role="presentation"` rule above it — purely visual, never
+in the keyboard order, never a heading. **The boundary is set where the list is built**: the
+module that decides the option order marks the divider-carrying option (e.g.
+`chartThemeOptions` stamps the first preset); a consumer must never recompute a group
+boundary by index arithmetic, which silently misplaces when the producer's ordering changes.
 The single-open registry means **disclosures cannot nest**: a SelectControl inside a
 settings popover would close — and unmount — its own parent on open. A control that needs
 its own popover sits beside the gear in the pane header, never inside the panel.