Add pre-aggregates incompatibility warning for personal warehouse connections (#536)

* Add warning that pre-aggregates are incompatible with personal warehouse connections

Generated-By: mintlify-agent

* Simplify personal warehouse connections warning to bare bones

Generated-By: mintlify-agent

---------

Co-authored-by: mintlify[bot] <109931778+mintlify[bot]@users.noreply.github.com>

Author: mintlify[bot]

references/pre-aggregates/overview.mdx

@@ -108,6 +108,12 @@ Pre-aggregates support metrics that can be re-aggregated from pre-computed resul
 - `max`
 - `average`
 
+### Personal warehouse connections
+
+<Warning>
+  Pre-aggregates are **not compatible** with [personal warehouse connections](/references/workspace/personal-warehouse-connections). Materialization always runs under a single user's credentials, so warehouse-level access rules are not applied per viewer. If you rely on personal warehouse connections to enforce data access, use [results caching](/guides/developer/caching) instead.
+</Warning>
+
 ### Current limitations
 
 Not all metrics work this way. Consider `count_distinct` with the same daily pre-aggregate from above. If a daily pre-aggregate stores "2 distinct customers on 2024-01-15" and "1 distinct customer on 2024-01-16", you can't sum those to get the monthly distinct count — Alice ordered on both days and would be counted twice: