docs: replace invalid config get examples

[davidmosiah]

Summary

• replace the three documented hermes config get <key> examples with the supported hermes config show command
• clarify where skill settings and session/model values can be inspected from the CLI

Fixes #30195.

Verification

• rg -n "hermes config get" website/docs returns no matches
• git diff --check

[alt-glitch]

Duplicate of #30293 (first open PR fixing #30195). Also competes with #30349 and #30390. All four PRs touch the same 3 doc files with the same fix.

[davidmosiah]

Thanks for the pointer. Closing this as a duplicate of #30293 and the other existing fixes for #30195.