deploy: clarify container path = where your code reads/writes

Make the volume mapping explicit: the right-hand mount path is where the
app writes. WORKDIR is /app, so code writing to ./cache lands in /app/cache
(this mount); same for /app/logs and /app/config. Removes ambiguity about
which side of the volume line the code targets.

Verified: mkdocs build --strict clean.
Signed-off-by: disqualifier <dev@disqualifier.me>

docs/deploy.md

@@ -155,8 +155,12 @@ volumes:
     The deploy layer injects `MOUNTS_DIR` and auto-creates the dir — but you
     **uncomment** the line and pick the container path (`/app/data` here), since
     that's app-specific and can't be auto-mounted.
-7.  Named volume with a **bare name** — ephemeral, auto-namespaced per service at
-    deploy time so it can't collide.
+7.  Named volume mounted at **`/app/cache`** — ephemeral scratch. The **right-hand
+    path is where your code writes**: `WORKDIR` is `/app`, so if your app writes to
+    `./cache` (or `/app/cache`), that's this mount. Same rule for logs (`/app/logs`)
+    and config (`/app/config`) — match the container path to where your code reads
+    and writes. The volume name is a bare name, auto-namespaced per service at deploy
+    so it can't collide.
 8.  Declare bare (`cache`, not `myapp_cache`). Deploy auto-prefixes it.
 
 !!! tip "Three tiers of storage"