fix(editor): improve block drag-and-drop hit targeting

[zacharias-ona]

Problem

Dragging blocks via the grip handle is finicky — the cursor must be positioned on the exact line of a block for the drop indicator to appear. Moving the cursor into the gap between blocks causes the target to vanish, making reordering unreliable.

Root cause

Two issues in getBlockElement:

1. Dead zone too small (4px) — Block elements have small margins (mt-0.5), so the gaps between them are larger than 4px. The cursor frequently lands in "no man's land" where no block is matched.
2. No fallback during drag — When the cursor is between blocks, the function returns null instead of snapping to the nearest block. This causes the drop indicator to disappear and the drop to fail.

Changes

• Increase HANDLE_DEAD_ZONE from 4px to 16px so the drag handle appears more readily when hovering near a block
• Add a nearest-block fallback: when no block matches within the dead zone, find the absolute nearest block by edge distance
• During drag operations (DRAGOVER_COMMAND / DROP_COMMAND), always use unbounded search so the cursor always resolves to a target
• Extract getTopLevelBlockElements helper to avoid duplicating the element lookup across the two search passes

Closes #99

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
memo	Ready	Preview, Comment	Apr 16, 2026 6:40pm

[zacharias-ona]

✅ UI verification passed — design spec compliance confirmed.

Static analysis — src/components/editor/draggable-block-plugin.tsx:

• Color tokens: text-muted-foreground, hover:text-foreground, bg-accent — all from the design spec token set
• Drop indicator: h-0.5 bg-accent matches spec (2px bg-accent line)
• Drag handle: GripVertical with text-muted-foreground matches spec
• Transitions: transition-opacity duration-100 — no decorative animations
• Accessibility: aria-label, role="button", tabIndex={0} present
• No arbitrary hex/rgb values, no arbitrary spacing

Visual verification (Playwright screenshots of editor page):

• Desktop dark: layout, spacing, colors, sidebar all correct
• Mobile (375×812): sidebar hidden, hamburger visible, editor full-width, no horizontal scroll

Changes are logic-only (hit-testing improvements for drag-and-drop targeting) with no visual impact at rest.

[zacharias-ona]

✅ Post-merge verification passed.

E2E suite: 27/27 tests passed (auth, editor drag-and-drop, editor links, slash commands, floating toolbar, page CRUD, sidebar drag-and-drop, workspace switcher).

Ad-hoc smoke tests:

• ✅ Landing page — loaded, has title
• ✅ /sign-in — rendered with email input
• ✅ /api/health — healthy
• ✅ Authenticated login flow — redirected to workspace
• ✅ Workspace page — fully loaded
• ✅ Editor navigation — page opened via sidebar, editor rendered
• ✅ No console errors (unauthenticated or authenticated)

No routes skipped.