Update FloorPlan spec: fix coord mapping, clamping, pointercancel, label placement

docs/superpowers/specs/2026-03-14-floorplan-design.md

@@ -38,7 +38,9 @@ Gradio Custom Component (Svelte + SVG), integrated as a first-class `gr.Componen
 }
 ```
 
-Coordinates are in pixels, matching the SVG viewport.
+`localisation` index mapping: `[0]=ymin`, `[1]=xmin`, `[2]=ymax`, `[3]=xmax`.
+
+Coordinates are in pixels, matching the SVG viewport. Input coordinates are assumed to fit within the fixed SVG viewport — behavior for out-of-bounds input is undefined.
 
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@@ -67,8 +69,9 @@ SVG rect: `x = xmin`, `y = ymin`, `width = xmax - xmin`, `height = ymax - ymin`.
 ## Drag Interaction
 
 1. `pointerdown` on a furniture `<g>` → mark as active, record pointer start position, apply highlight style (distinct stroke color + increased opacity)
-2. `pointermove` on the `<svg>` → update active furniture's `(dx, dy)` offset in real time
-3. `pointerup` anywhere → clear active state, compute new absolute `localisation` = original box coords + `(dx, dy)` offset, emit updated `furnitures` to Gradio
+2. `pointermove` on the `<svg>` → update active furniture's `(dx, dy)` offset in real time; clamp so the box stays fully within the SVG viewport
+3. `pointerup` anywhere → clear active state, compute new `localisation`: `new_xmin = xmin + dx`, `new_ymin = ymin + dy`, `new_xmax = xmax + dx`, `new_ymax = ymax + dy` (preserving `(ymin, xmin, ymax, xmax)` order), then emit updated `furnitures` to Gradio
+4. `pointercancel` → revert the furniture to its original position, clear active state, do not emit
 
 Highlight state: active box gets a contrasting stroke color (e.g. orange) so the user clearly sees what is being moved.
 
@@ -104,7 +107,7 @@ Highlight state: active box gets a contrasting stroke color (e.g. orange) so the
 - Room polygon: dark stroke (`#333`), no fill, stroke-width 2
 - Furniture rect (default): semi-transparent fill (e.g. `rgba(100, 149, 237, 0.3)`), colored stroke
 - Furniture rect (active/dragging): orange stroke (`#f97316`), higher opacity
-- Label text: small, centered above or inside the rect, dark color
+- Label text: small, centered inside the rect, dark color
 
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@@ -114,3 +117,4 @@ Highlight state: active box gets a contrasting stroke color (e.g. orange) so the
 - Snapping furniture to walls or grid
 - Multi-select or grouping furniture
 - Persisting positions beyond the Gradio session
+- Input coordinates outside the fixed SVG viewport bounds