Support Nushell

[0x4D5352]

Checks

• I have searched github.com/aws/amazon-q-developer-cli/issues and there are no duplicates of my issue
• I have run q doctor in the affected terminal session
• I have run q restart and replicated the issue again

Operating system

macOS 26.2.0 (25C56)

Expected behaviour

When using ssh or other commands that Kiro integrates with using its own command substitutions, it should properly support the syntax expected by nushell (e.g. replacing && with ;).

Actual behaviour

~ > ssh MY-REMOTE-HOST
Error: nu::parser::shell_andand

  x The '&&' operator is not supported in Nushell
   ,-[source:1:21]
 1 | command -v kiro-cli && kiro-cli internal generate-ssh --remote-host MY-REMOTE-HOST --remote-port 22 --remote-username MY-USERNAME
   :                     ^|
   :                      `-- instead of '&&', use ';' or 'and'
   `----
  help: use ';' instead of the shell '&&', or 'and' instead of the boolean '&&'```

### Steps to reproduce

1. Launch a Nushell session (e.g. `nu`)
2. Install the Kiro SSH integration with `kiro-cli integrations install ssh`
3. Attempt to SSH into a remote host
4. Observe the warning output.

### Environment

```yaml
[q-details]
version = "1.23.1"
hash = "faddc2c7ee17078025a62a8dfad6543a4154d2fa"
date = "2025-12-23T23:07:20.579821Z (10d ago)"
variant = "full"

[system-info]
os = "macOS 26.2.0 (25C56)"
chip = "Apple M3 Pro"
total-cores = 12
memory = "36.00 GB"

[environment]
cwd = "/Users/USER"
cli-path = "/Users/USER"
os = "Mac"
shell-path = "/Users/USER/.cargo/bin/nu"
shell-version = "0.109.1"
terminal = "Ghostty"
install-method = "unknown"

[env-vars]
PATH = "/opt/homebrew/bin:/opt/homebrew/sbin:/opt/homebrew/opt/postgresql@16/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Applications/Ghostty.app/Contents/MacOS:/usr/local/bin:/Users/USER/.local/bin:/Users/USER/.local/share:/Users/USER/.cargo/bin:/Users/USER/go/bin:/Users/USER/.cabal/bin:/Users/USER/.toolbox/bin"
SHELL = "/Users/USER/.cargo/bin/nu"
TERM = "xterm-ghostty"
__CFBundleIdentifier = "com.mitchellh.ghostty"