feat(collections): show a dataset's JSON schema in a modal - #364

What

Adds a Schema button to every row of the datasets catalog (both table and card views). It opens the collection's published JSON Schema — GET /ogcapi/collections/{id}/schema?f=json — as a readable field table: name, title, OGC role, type, description, and enum values. A Raw JSON toggle and a copy button cover the case where the document itself is what the reader wants.

Also hides the desktop-GIS surfaces on this page (see below).

Why the field table is the default view

The server fills in per-property title and description for these collections, and a raw JSON dump buries them. The schema is read far more often to answer "what columns does this dataset have and what do they mean" than to be copied verbatim — so the readable view leads and the raw document is one toggle away.

Shape details the renderer has to handle

• A geometry property arrives with a format (geometry-any) and no type, so the type label falls back to format.
• Controlled vocabularies run to two dozen entries; enum chips are capped at six with the remainder behind a tooltip.
• Below the tablet breakpoint the three-column table pushes descriptions off-screen, so narrow screens get a stacked per-field layout instead.
• The dialog keeps its target through MUI's closing transition — clearing it on close flashed an empty "0 fields" shell on the way out.

Hand-written zod, deliberately

collectionSchema.ts hand-writes the schema types, the same way gisArtifacts.ts does. The committed openapi-auth.json snapshot describes none of the /ogcapi paths, so src/generated cannot describe this response. Replace with generated schemas once the OGC surface lands in the deployed spec.

Desktop GIS hidden

The connections panel, the table's Desktop GIS column, and the per-card download links are now gated behind a single SHOW_DESKTOP_GIS = false constant in list.tsx. The catalog data still loads (the collection index keys off it), so flipping the constant back to true restores all three together. The table's last column is renamed Map → Actions and the group-band colSpan follows the flag.

The sidebar's "Connect Desktop GIS" link is a separate page and is untouched.

Verification

• npm run typecheck clean.
• npm run test:run — 434 passed, 1 skipped, including 13 new tests across collectionSchema.test.ts and CollectionSchemaDialog.test.tsx.
• Lint clean on changed files. The one warning in list.tsx (sortOgcCollections unused) is pre-existing on staging.
• Exercised in the browser against the local API at desktop and mobile widths: modal opens from both views, both toggles render, close is clean, no console errors.

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