docs: update spec and guide for search position and chevron removal

- COMPONENT_GUIDE: note search renders between Header and Sections,
  no chevrons on section headers
- Spec: update rendering diagrams and description to match
  implemented behavior

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

COMPONENT_GUIDE.md

@@ -114,8 +114,11 @@ Sidebar compound API:
     </Sidebar.Footer>
   </Sidebar>
 
-The app controls all content — sections, order, tree data, collapse state.
-Sidebar provides the frame, search input, and icon-rail collapse mode.
+Notes:
+- Search input auto-renders between Header and first Section (not above Header)
+- Section headers have no chevron — the entire row is clickable to toggle
+- The app controls all content — sections, order, tree data, collapse state
+- Sidebar provides the frame, search input, and icon-rail collapse mode
 ```
 
 ### Data page pattern

docs/superpowers/specs/2026-04-02-composable-sidebar-design.md

@@ -73,6 +73,7 @@ The outer shell. Renders the sidebar frame with an optional search input and col
 - Width transition: `transition: width 200ms ease`
 - Collapse toggle button (`<<` / `>>` chevron) in top-right corner
 - Search input hidden when collapsed
+- Search input auto-positioned between `Sidebar.Header` and first `Sidebar.Section` (not above Header)
 
 ### `<Sidebar.Header>`
 
@@ -119,13 +120,13 @@ An accordion section with a collapsible header and content area.
 
 **Expanded rendering:**
 ```
-v [icon] APPLICATIONS
+[icon] APPLICATIONS
   (children rendered here)
 ```
 
 **Collapsed rendering:**
 ```
-> [icon] APPLICATIONS
+[icon] APPLICATIONS
 ```
 
 **In sidebar icon-rail mode:**
@@ -133,7 +134,7 @@ v [icon] APPLICATIONS
 [icon]     <- centered, tooltip shows label on hover
 ```
 
-Header has: chevron (left), icon, label. Chevron rotates on collapse/expand. Active section gets the amber left-border accent (existing pattern). Clicking the header calls `onToggle`.
+Header has: icon and label (no chevron — the entire row is clickable). Active section gets the amber left-border accent (existing pattern). Clicking anywhere on the header row calls `onToggle`.
 
 **Implementation detail:** `Sidebar.Section` and `Sidebar.Header` need to know the parent's `collapsed` state to switch between expanded and icon-rail rendering. The `<Sidebar>` component provides `collapsed` and `onCollapseToggle` via React context (`SidebarContext`). Sub-components read from context — no prop drilling needed.