fix(helm): correct the ui.env description, and default it to a list

The comment described `ui.env` as key-value pairs for a ConfigMap. It is neither:
`ui-deployment.yaml` splices it into the UI container's own `env:` list, so it
takes `{name, value}` entries and reaches no ConfigMap. The default changes from
`{}` to `[]` for the same reason — both are falsy to the `with` guard, so nothing
renders differently, but the type is no longer misstated.

This is the field an installed app extension's settings go in, so the note now
says so.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: Nicholas Bucher <behappy54321@gmail.com>

Author: Charlesthebird

helm/kagent/values.yaml

@@ -442,7 +442,11 @@ ui:
     proxyReadTimeout: 1800s
     # -- proxy_send_timeout: max time between two successive writes to the upstream.
     proxySendTimeout: 1800s
-  env: {} # Additional configuration key-value pairs for the ui ConfigMap
+  # -- Extra environment variables for the UI container, spliced into its `env:`
+  # list verbatim. A list of `{name, value}` entries, not a map. An installed app
+  # extension's own settings go here, named `EXTENSION_*`; the container's startup
+  # script copies those onto `window.environmentVariables` for the browser to read.
+  env: []
   # -- Identity headers the UI's nginx proxy will forward to the backend on
   # /api/ and /a2a/. Names are case-insensitive. Authorization is always
   # forwarded; the auth-proxy identity headers (x-auth-request-*, x-forwarded-user,