deploy: fix vanishing commented mounts line in compose annotations

A '# (6)!' annotation marker on a fully-commented YAML line made Material's
annotation JS swallow the whole line into the tooltip — so the commented
'# - ${MOUNTS_DIR...}' line disappeared, leaving an orphan marker with no
visible code (which is why '(6)' seemed missing).

Fix: drop the marker from the commented line, keep it as plain visible YAML
('# optional — see below'), and move its explanation to prose below the
annotation list. Renumber cache/volume markers 7->6, 8->7.

Verified in-browser: commented mounts line now renders visibly; no orphan
marker. build --strict clean.

Signed-off-by: disqualifier <dev@disqualifier.me>

docs/deploy.md

@@ -134,11 +134,11 @@ services:
     volumes:
       - ${LOGS_DIR:-./logs}:/app/logs        # (4)!
       - ${CONFIG_DIR:-./config}:/app/config  # (5)!
-      # - ${MOUNTS_DIR:-./mounts}:/app/data  # (6)!
-      - cache:/app/cache                     # (7)!
+      # - ${MOUNTS_DIR:-./mounts}:/app/data  # optional — see below
+      - cache:/app/cache                     # (6)!
 
 volumes:
-  cache:                                     # (8)!
+  cache:                                     # (7)!
 ```
 
 1.  The service key is always **`svc`** — never a repo-specific name, never a
@@ -151,17 +151,18 @@ volumes:
 4.  Logs → host (**output**), path **injected** by the deploy layer. The `:-./logs`
     default lets you `docker compose up` locally with nothing set and still work.
 5.  Config → host (**input you edit**), likewise injected.
-6.  **Optional, commented by default.** A host dir for arbitrary read/write data.
-    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 mounted at **`/app/cache`** — ephemeral scratch. The **right-hand
+6.  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.
+7.  Declare bare (`cache`, not `myapp_cache`). Deploy auto-prefixes it.
+
+The commented **`${MOUNTS_DIR}`** line is the optional third tier — a host dir for
+arbitrary read/write data. The deploy layer injects `MOUNTS_DIR` and auto-creates the
+dir, but the mount line is **opt-in**: uncomment it and pick the container path
+(`/app/data` above) yourself, since that's app-specific and can't be auto-mounted.
 
 !!! tip "Three tiers of storage"
     - **`logs`** (output) and **`config`** (input you edit) — **we handle these**: