Fix feature/layer styles dropped on import until refresh

[ThomasHalwax]

Problem

When a layer is imported (drag & drop or paste), feature geometries appear
immediately on the map but their styling (e.g. line colour and width) only
becomes visible after a refresh.

Root cause

store.insert emits a single batch containing both the feature: entries
and their style+feature: entries. featureSource's batch ordering (ord)
deliberately processes put style+ (ord 2) before put feature (ord 3),
so that the feature created afterwards can read its initial style from
state.styles inside readFeature.

But the featureStyle and layerStyle handlers only ever deleted from
state.styles (on del) and never wrote to it on put. So on import:

1. the style event fires first, finds no live feature yet (getFeatureById
   returns undefined) and discards the signal update;
2. state.styles still holds the dictionary loaded once at startup, so the
   feature created next initialises with an empty style.

The style only appears after a refresh, when the init block re-reads
store.dictionary('style+') from the now-persisted entries.

Fix

Update state.styles[key] on put in both the featureStyle and
layerStyle handlers, matching the intent of the existing batch ordering.
No behaviour change for the already-working in-app editing path.

Testing

• Imported a layer with per-feature style+feature: entries -> styling now
  renders immediately, no refresh needed.
• Editing feature/layer styles on existing features continues to work.