style(explorer): improve upgrade warning clarity and formatting

Use semantic line feeds, replace bold text with heading in callouts,
explain the root cause (root-owned volumes), and use standard callout
syntax for the release notes upgrade notice.

Author: jstirnaman

content/influxdb3/explorer/install.md

@@ -214,23 +214,30 @@ docker-compose up -d
 > Without a mounted `./db` directory, application data is lost when the container is deleted.
 
 > [!Warning]
-> **Upgrading from Explorer v1.6.x or earlier?**
+> #### Upgrade from Explorer v1.6.x or earlier
 >
-> Starting with v1.7.0, the Explorer container runs as a non-root user (`influxui`, uid 1500) for improved security. If you're upgrading from an older version with existing mounted volumes, you'll need to update file ownership.
+> Starting with v1.7.0, the Explorer container runs as a non-root user
+> (`influxui`, uid 1500) for improved security. Because earlier versions
+> ran as root, existing mounted volumes are owned by root — and the new
+> non-root process can't access them.
+>
+> If you start the upgraded container without updating file ownership,
+> it exits with the following error:
 >
-> When you start the upgraded container, you may see an error like:
 > ```
 > ERROR: Directory '/db' is owned by root and not accessible to the 'influxui' user.
 > ```
 >
-> To fix this, change ownership of your mounted directories to uid 1500:
+> To prevent or resolve this error, change ownership of your mounted
+> directories to uid 1500 before you start the container:
 >
 > ```bash
 > sudo chown -R 1500:1500 /path/to/your/db
-> sudo chown -R 1500:1500 /path/to/your/config  # if using config volume
+> sudo chown -R 1500:1500 /path/to/your/config
 > ```
 >
-> After updating ownership, restart the container. Fresh installations are unaffected.
+> After you update ownership, restart the container.
+> Fresh installations are unaffected.
 
 ### Pre-configure InfluxDB connections
 

content/influxdb3/explorer/release-notes/_index.md

@@ -22,18 +22,24 @@ docker pull influxdata/influxdb3-ui
 
 - **Container user change**: The Docker container now runs as non-root user `influxui` (uid 1500) instead of root for improved security.
 
-  **Action required for upgrades:** If you're upgrading from v1.6.x or earlier with mounted volumes (e.g., `/db`, `/app-root/config`), you must update file ownership before the container will start:
-
-  ```bash
-  sudo chown -R 1500:1500 /path/to/your/db
-  sudo chown -R 1500:1500 /path/to/your/config
-  ```
-
-  The container will exit with a clear error message and instructions if it detects root-owned files. Fresh installations are unaffected.
+> [!Important]
+> #### Action required for upgrades
+>
+> If you're upgrading from v1.6.x or earlier with mounted volumes
+> (for example, `/db` or `/app-root/config`), update file ownership
+> before you start the container:
+>
+> ```bash
+> sudo chown -R 1500:1500 /path/to/your/db
+> sudo chown -R 1500:1500 /path/to/your/config
+> ```
+>
+> The container exits with an error message if it detects root-owned
+> files. Fresh installations are unaffected.
 
 #### Features
 
-- **Security**: Container now runs as non-root user (uid 1500) for improved security posture.
+- **Non-root container**: The container now runs as a non-root user (uid 1500) for improved security.
 
 ## v1.6.3 {date="2026-02-19"}