Tool suggest still misfires when model needs tool_search, updating the
prompts to further disambiguate it:
- [x] rename it from `tool_suggest` to `request_plugin_install`
- [x] rephrase "suggestion" to "install" in the tool descriptions.
- [x] disambiguate "the tool" vs "the plugin/connector".
Tested with the Codex App and verified it still works.
