docs(05-02): complete pdf-fill-and-field-mapping plan 02

- FieldPlacer.tsx: dnd-kit drag-and-drop field placer with Y-flip coordinate conversion
- PdfViewer.tsx: extended with pageInfo state and FieldPlacer integration
- @dnd-kit/core and @dnd-kit/utilities installed
- Fields persist via PUT /api/documents/[id]/fields on every add/remove
- 05-02-SUMMARY.md created, STATE.md and ROADMAP.md updated

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

.planning/phases/05-pdf-fill-and-field-mapping/05-02-SUMMARY.md

@@ -0,0 +1,92 @@
+---
+phase: 05-pdf-fill-and-field-mapping
+plan: 02
+subsystem: frontend/documents
+tags: [dnd-kit, pdf-fields, field-placer, coordinate-conversion, drag-and-drop]
+dependency_graph:
+  requires: [05-01]
+  provides: [field-placement-ui, signature-field-overlay]
+  affects: [documents-detail-page, pdf-viewer]
+tech_stack:
+  added: ["@dnd-kit/core@^6.3.1", "@dnd-kit/utilities@^3.2.2"]
+  patterns: [dnd-kit-drag-overlay, y-flip-coordinate-conversion, droppable-pdf-zone]
+key_files:
+  created:
+    - teressa-copeland-homes/src/app/portal/(protected)/documents/[docId]/_components/FieldPlacer.tsx
+  modified:
+    - teressa-copeland-homes/src/app/portal/(protected)/documents/[docId]/_components/PdfViewer.tsx
+decisions:
+  - "DragOverlay used for ghost rendering during drag — avoids transform-based dragging which breaks coordinate math relative to the droppable container"
+  - "containerRef.getBoundingClientRect() called at drop time (not stale pageInfo.width) — captures current rendered size after zoom changes"
+  - "activatorEvent + delta pattern for final drop coordinates — activatorEvent gives the client position where drag started, delta gives displacement"
+  - "DroppableZone assigns both setNodeRef (dnd-kit) and containerRef (coordinate math) to same DOM node via combined ref callback"
+  - "top: top - heightPx applied to overlay divs — pdfToScreenCoords returns y of bottom-left corner, must shift up by field height for DOM top-left origin"
+metrics:
+  duration: 1 min
+  completed_date: "2026-03-20"
+  tasks_completed: 2
+  files_created: 1
+  files_modified: 1
+---
+
+# Phase 5 Plan 02: Drag-and-Drop Signature Field Placer Summary
+
+**One-liner:** dnd-kit DndContext with draggable palette token + droppable PDF zone; Y-flip coordinate conversion persists fields to DB via PUT /api/documents/[id]/fields.
+
+## What Was Built
+
+A complete drag-and-drop field placement system integrated into the document detail page:
+
+1. **FieldPlacer.tsx** (321 lines) — New client component providing:
+   - A `DndContext` wrapping both palette and PDF canvas
+   - `DraggableToken` sub-component using `useDraggable` for the "Signature Field" palette item
+   - `DroppableZone` sub-component using `useDroppable` to make the PDF canvas a valid drop target
+   - `DragOverlay` showing a blue ghost rectangle during drag
+   - `screenToPdfCoords()` — Y-flip formula converting DOM coordinates to PDF user space
+   - `pdfToScreenCoords()` — inverse formula for rendering stored fields as overlays
+   - Server sync: GET on mount (load existing), PUT on every add/remove (persist)
+   - Per-page filtering (`field.page === currentPage`) so page 1 fields don't show on page 2
+
+2. **PdfViewer.tsx** (updated) — Extended with:
+   - `pageInfo` state (`PageInfo | null`) populated via `onLoadSuccess` callback
+   - `Math.max(page.view[0], page.view[2])` / `Math.max(page.view[1], page.view[3])` for robust `originalWidth`/`originalHeight` (handles non-standard mediaBox ordering)
+   - `FieldPlacer` wraps the `Document`/`Page` tree, receiving `docId`, `pageInfo`, `currentPage`
+   - Only `scale` prop used on `<Page>` (not both `width` + `scale`)
+
+## Verification Results
+
+- `npm run build` — compiled successfully (both tasks)
+- FieldPlacer.tsx: 321 lines (minimum 80 required)
+- `@dnd-kit/core` and `@dnd-kit/utilities` present in package.json
+- PdfViewerWrapper.tsx unchanged (dynamic import wrapper still passes docId through)
+
+## Coordinate Conversion Details
+
+The Y-flip formula is critical for correct field placement:
+- **DOM**: Y=0 at top, increases downward
+- **PDF user space**: Y=0 at bottom, increases upward
+- `pdfY = ((renderedH - screenY) / renderedH) * originalHeight`
+- This means dragging to the visual top of a page stores a high pdfY value (near originalHeight)
+- `containerRect.width/height` used at drop time (not stale pageInfo) to handle zoom changes correctly
+
+## Commits
+
+| Task | Commit | Description |
+|------|--------|-------------|
+| Task 1 | 6069ae5 | feat(05-02): install dnd-kit and create FieldPlacer component |
+| Task 2 | 7a36736 | feat(05-02): extend PdfViewer with pageInfo state and FieldPlacer integration |
+
+## Deviations from Plan
+
+None — plan executed exactly as written.
+
+The DroppableZone component uses a combined ref callback to assign both the dnd-kit `setNodeRef` and the `containerRef` simultaneously to the same DOM node — this was a minor implementation detail not explicitly specified in the plan but required for correct operation.
+
+## Self-Check: PASSED
+
+- FOUND: FieldPlacer.tsx (321 lines)
+- FOUND: PdfViewer.tsx (updated)
+- FOUND commit: 6069ae5
+- FOUND commit: 7a36736
+- @dnd-kit/core and @dnd-kit/utilities in package.json
+- Build: compiled successfully