PYR1-1801 Publish shapefile layers without an auto-published copy

[danielhvs]

Purpose

Each shapefile store now publishes exactly one feature type, named after the store. Before this, every fire spread workspace ended up with isochrones1 to isochrones4 next to the intended elmfire_landfire_{30,50,70,90}_isochrones, and every match-drop workspace with 6 isochrones_md-<id>_<ts>_<pct>1 copies.

Env	Leaked feature types
dev	44 on geoserver02
prod	44 on geoserver02, 217 on geoserver03 (match-drop)

Cause

1. The :shapefile branch sent PUT .../external.shp, and GeoServer auto-publishes a feature type named after the shapefile basename.
2. Requests go out in phases, so all of a workspace's external.shp PUTs run in parallel. Several shapefiles share a basename: 5 × isochrones.shp per fire since PYR1-1579's rename, and ELMFIRE and Pyretechnics ship the same isochrones_md-..._<pct>.shp per match-drop run. GeoServer suffixes all but the first.
3. The cleanup renamed and deleted by the unsuffixed name, so it removed one copy and returned 404 for the rest. Prod trinity logged 116 404 ...:isochrones on 09-23.

Changes

1. :shapefile creates the store, then POSTs a single feature type with name = store name and nativeName = shapefile basename (rest/create-feature-type-alias, the same request the rename step already sent). The auto-publishing PUT and the two cleanup DELETEs are gone.
2. Flat shapefiles, where store name = basename, use the same single POST.
3. :geopackage is unchanged. Its table names are unique per store, so it has no collision.
4. shapefile-layer-specs-test covers the nested and flat cases and the style step.

Existing leaked layers are not touched. Fire spread workspaces rotate out on their own; match-drop ones need a one-off cleanup per environment after this ships.

Verified on dev

I pinned the dev GeoSync UberJAR to 9565a00, removed fire-spread-forecast_wa-sisi_20260924_095400, and re-added it with herd trigger sync-fire-spread-forecast:

1. Each elmfire_landfire_{10..90}_isochrones store holds one feature type. There are no isochronesN copies, and geoserver02's leak count dropped from 44 to 40 (wa-sisi is gone from the list)
2. The workspace has 30 catalog layers (5 feature types + 25 coverages), down from 34
3. Trinity log: Workspace updated. with 0 404 ...:isochrones
4. All 5 layers keep nativeName isochrones and SRS EPSG:32610, get real bboxes that widen from P10 to P90, render WMS GetMap 200 image/png, and have GWC tile layers at [1, 1] with MVT

Layer	latLon bbox	GetMap
elmfire_landfire_10_isochrones	-120.881,48.328,-120.763,48.405	200 png 13.7 KB
elmfire_landfire_30_isochrones	-120.894,48.327,-120.757,48.410	200 png 13.1 KB
elmfire_landfire_50_isochrones	-120.901,48.324,-120.752,48.414	200 png 13.1 KB
elmfire_landfire_70_isochrones	-120.906,48.321,-120.715,48.414	200 png 14.3 KB
elmfire_landfire_90_isochrones	-120.927,48.310,-120.684,48.426	200 png 16.4 KB

Related Issues

Closes PYR1-1801
Relates to PYR1-1579, PYR1-1786