perf(bundle): load the space-card GUI editor lazily to keep #744 under the initial View budget (#744)

The floor-geometry key of #744 (+~143 B gzip) put the initial View graph at
301 097 B gzip, 31 B over the absolute 301 066 B wall in
scripts/bundle-budget.mjs. The comment over that wall says the next growth
is paid by moving code into lazy graphs, not by raising the budget.

`src/space-card.ts` imported its Lovelace GUI config editor
(`src/space-editor.ts`, the `houseplan-space-card-editor` element)
statically, so every View paid for a form only the dashboard editor opens.
`getConfigElement()` now imports it on demand, exactly as
`houseplan-card.getConfigElement()` already does for `./editor`; Home
Assistant awaits the returned promise. The editor's dependencies (lit, i18n,
space-geometry) stay in the shared chunk, so the new `space-editor-*.js`
chunk holds only the element itself (~1.1 KB gzip).

Measured: initial View 301 097 -> 300 489 B gzip (-608 B), headroom to the
301 066 B budget 577 B. The beta ceiling (300 142 B, band 2 000 B above it,
#699) and the budget are unchanged; lazy editor/onboarding graphs are not
touched.

Issue: #744
User-Visible: no
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018qZfe7YS4rqEMKoVeS3GKd

src/space-card.ts

@@ -46,7 +46,6 @@ import {
   createGlowRuntimeState, disposeGlowRuntime,
   type GlowRuntimeHost, type GlowRuntimeState,
 } from './glow-scene';
-import './space-editor';
 import {
   DECOR_ASSETS_API_VERSION, decorAssetIds, resolveDecorAssets, type DecorAsset,
 } from './decor-assets';
@@ -276,7 +275,10 @@ class HouseplanSpaceCard extends LitElement {
     this._connHooked = connection;
   }
 
-  public static getConfigElement() {
+  /** The Lovelace GUI editor is a lazy chunk, as for `houseplan-card` (#744):
+   *  only the dashboard editor asks for it, never the first View frame. */
+  public static async getConfigElement() {
+    await import('./space-editor');
     return document.createElement('houseplan-space-card-editor');
   }