docs: move service issue notes from READMEs into docs/<service>

Service READMEs now cover only what the service is and how to deploy it.
Known issues, log noise and troubleshooting move to docs/<service>/, named
after the service directory, so editing them never redeploys the service.
Drop alloy's validate workflow, which never ran from a subdirectory.

opencode/README.md

@@ -31,13 +31,6 @@ and survive a redeploy.
 Then open the domain and sign in with `OPENCODE_SERVER_USERNAME` and
 `OPENCODE_SERVER_PASSWORD`.
 
-The container logs a Bun stack trace ending in
-`Executable not found in $PATH: "xdg-open"` on every start. `opencode web`
-tries to open the UI in a local browser; there isn't one. It is noise — the
-server is already listening by then, and the container keeps running.
-Installing `xdg-utils` would silence it at the cost of pulling X11 in and
-tripling the image, which is not worth it for a log line.
-
 ## Authentication
 
 `OPENCODE_SERVER_PASSWORD` is the only thing between the domain and a shell on