Issue Summary: 

Warnings displayed in the CLI (e.g. about node version requirements) are sent to stdout, which means if –-json option is being used, a command may produce non-json output.  

Steps to Reproduce

Example:

1. Use node version that is later than the supported CLI versions and download forge cli (e.g. node 24, cli version 12.13.0)
2. Run a command with --json option piped to use the json output , e.g. forge install list --json | jq

Expected Results

Warning should be visually displayed to stderr, with json output to stdout so it can still be piped (e.g. to jq).

Actual Results

$ forge install list --json | jq
jq: parse error: Invalid numeric literal at line 1, column 8

Workaround

No workaround known (other than addressing the cause of the warning).