docs: put MinIO first-class on ground, add executive overview

Treat MinIO as existing stack infrastructure (default T3 warehouse, not
on the drone), add a one-page executive map, and record placement as an
open team question rather than a rip-and-replace.

docs/12-design-journey.md

@@ -144,10 +144,13 @@ gives redundancy and a way to cross-check later. On the ground, when the fleet
 returns, the same path unifies every unit's data into a
 [local warehouse](06-environments.md). The warehouse is read-mostly for
 analytics, so transaction contention is not a concern, which opens a
-DuckDB / DuckLake approach with MinIO underneath, the
+DuckDB / DuckLake approach with **MinIO underneath on the ground (T3)** — MinIO
+is already in the stack, so the warehouse leans on it rather than inventing a
+second object store — the
 [same storage model on both ends](adr/ADR-0002-one-storage-format.md). One
 uniform structure is what lets an analyst trust a single picture even when a
-unit's data has a gap.
+unit's data has a gap. On-board MinIO stays an open exception, not the default
+([00 — Executive](00-executive.md)).
 
 > **Read the code**
 > - [`infra/terraform/ground/main.tf`](https://git.produktor.io/eSlider/swarm-house/src/branch/main/infra/terraform/ground/main.tf#L124-L160) — the post-flight T1 to T3 offload CronJob