fix(cli): make voice activation hints shell-safe and copy-pastable

[crrow]

Context

CLI output currently suggests commands with angle-bracket placeholders like kokoro:<voice>, which can be copied directly into zsh and interpreted as redirection.

Acceptance Criteria

• Update CLI guidance strings to use copy-pastable examples (no <...> shell metachar placeholders)
• Ensure RVC activation hint is directly runnable
• Update docs references that can mislead copy-paste usage