US-017 completed

progress.txt

@@ -295,3 +295,24 @@
   - Nord theme (`@milkdown/theme-nord`) provides base ProseMirror structure; override with CSS using the app's semantic color variables for consistent theming
   - Import both `@milkdown/theme-nord/style.css` and `@milkdown/kit/prose/view/style/prosemirror.css` for proper base styling
 ---
+
+## 2026-02-22 - US-017
+- What was implemented:
+  - Fluid Curtain pull-down animation in `AppShell.tsx`
+  - `framer-motion` `useMotionValue(0)` + `useSpring(y, { stiffness: 300, damping: 30 })` controls `y` CSS transform on a `motion.div` wrapping the content area inside `SidebarInset`
+  - Sidebar stays visible at all times — only content area slides down
+  - Trigger 1: `document` wheel event — `findScrollableAncestor()` walks DOM to detect nearest scrollable element; if `scrollTop === 0` and `deltaY < 0`, opens curtain (`y.set(window.innerHeight)`)
+  - Trigger 2: `Cmd/Ctrl+K` keyboard shortcut toggles curtain open/closed
+  - Closing: `deltaY > 0` while curtain is open, or `Cmd/Ctrl+K`
+  - `AIChatPanel` placeholder component at `src/renderer/components/ai/AIChatPanel.tsx` — absolute `z-0` layer behind the sliding content panel
+  - Right-edge label dynamically changes: `"scrolling up for Adiuva"` + `ChevronUp` when closed, `"back to app"` + `ChevronDown` when open
+  - App panel remains mounted during animation (no unmount/remount, no state loss)
+  - `curtainOpenRef` (useRef) keeps event handlers in sync without re-registering effects
+- Files changed: `src/renderer/components/layout/AppShell.tsx`, `src/renderer/components/ai/AIChatPanel.tsx` (new), `prd.json`, `progress.txt`
+- **Learnings for future iterations:**
+  - `SidebarInset` already has `relative` in its base classes — adding `overflow-hidden` via className prop is sufficient to clip the sliding `motion.div`
+  - `useMotionValue` + `useSpring` pattern: `y.set(target)` immediately sets the spring target; `springY` (from `useSpring`) animates toward it — apply `springY` to `style={{ y: springY }}`, not `y` directly
+  - `findScrollableAncestor()` DOM walk is needed because `body` and `#root` both have `overflow: hidden` — scroll detection must target inner route containers (e.g., `overflow-y-auto` divs in projects/tasks)
+  - `useRef` for curtain open state avoids stale closures in `useEffect` wheel/keyboard handlers — the boolean ref is updated synchronously alongside `useState` setter
+  - `{ passive: true }` on wheel listener is correct when not calling `preventDefault()` — avoids Chrome console warnings
+---