feat(init)!: install configured key bindings by default #47

Parent

Part of #43. Depends on #44, #45, and #46.

Summary

Make configured navigation key bindings part of normal shell initialization while retaining an explicit one-shot opt-out.

CLI behavior

cj init zsh                         # includes configured binding
cj init zsh --no-setup-key-binding  # wrapper/completion only

Acceptance criteria

• cj init <shell> installs the configured binding by default unless its behavior chain is empty
• add --no-setup-key-binding and expose it in generated CLI completions
• decide whether the old positive --setup-key-binding remains as a compatibility no-op or is removed before v1, and document the decision
• the opt-out affects only the configurable Ctrl/Alt+O binding, never cd -jw<Tab>
• dependency checks happen when the widget is invoked, allowing install/removal of zoxide or fzf without regenerating integration
• do not add cj --keybinding-rehash; TOML changes continue to use cj init <shell> -o <path> followed by reload/restart
• generated output remains deterministic for the same configuration
• README examples, migration notes, and Bash/Zsh/Nushell/PowerShell CLI completions reflect the new default