docs: describe materialized-view refresh as a full rebuild

Main now rebuilds a materialized view completely on every refresh
(#4373): there is no incremental mode, no `full` argument and no
stable-row-ID requirement on the source. The example ran against the
SDK built from this branch (0.40.0b13) failed, because a refresh after
adding Bea writes both matching rows, not one.

The example now creates its source with the default options and expects
two rows written by the refresh, and its generated snippet is
regenerated. Separate tests cover `with_no_data` (one matching row on
the first refresh) and refreshing to an earlier source version. The
refresh page explains the full rebuild and keeps the #incremental and
#stable-row-ids anchors for the sections that replace them. Its version
note now says what the published 0.39.0 does differently, as observed
with that release.

The management, table, database, limits, architecture and data-types
pages no longer say a view's source needs stable row ids, and the
feature-engineering and tutorial summaries no longer call refreshes
incremental.

docs/web/tutorials/index.mdx

@@ -38,5 +38,5 @@ are runnable in Colab; the rest are written up here.
 | [Multi-vector search](/search/vector-search) | Several embeddings per document. |
 | [Reranking](/reranking) | Reordering results to improve the top-k. |
 | [Feature engineering](/feature-engineering) | Deriving columns and tables from data already stored. |
-| [Materialized views](/management/materialized-view) | A table defined by a query, refreshed incrementally. |
+| [Materialized views](/management/materialized-view) | A table defined by a query, recomputed by each refresh. |
 | [Training](/training/data-loading) | Reading a table into a data loader. |