Milestone 72 phase B — Grafana-style drag-resize grid for dashboard widgets:
- DashboardWidget: replace `position` with a 12-col grid placement
(grid_x/grid_y/grid_w/grid_h). Migration 0021 backfills the old position
order into a 3-up grid (4 cols x 4 cells each) and drops position.
- View + share render a static CSS grid from x/y/w/h: fixed cell height
(h * 70px) with the body scrolling, so the arranged layout is what's shown;
collapses to a single column under 820px.
- Edit view: Gridstack.js 12.6.0 (vanilla, CDN, pinned) — drag the title bar
to move, drag a corner/edge to resize; every change autosaves to a new
/d/<id>/edit/layout endpoint. Replaces the SortableJS position reorder.
- add_widget appends at the bottom-left; remove no longer renumbers.
_get_widgets now orders by grid position (drives DOM + mobile fallback order).
Note: Gridstack drag-resize is browser-only, so CI can't exercise it — needs an
operator visual check of the edit experience.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
