Add support for /bin/tcsh

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue
- [x] I have run `q doctor` in the affected terminal session
- [x] I have run `q restart` and replicated the issue again

### Operating system

macOS 15.6.1 (24G90)

### Expected behaviour

q doctor provides no errors when using /bin/tcsh

### Actual behaviour

✘ Compatible shell: Default shell UserShell: /bin/tcsh incompatible

✘ Doctor found errors. Please fix them and try again.

### Steps to reproduce

_No response_

### Environment

```yaml

[q-details]
version = "1.16.1"
hash = "dad39a19a27fba493d42acb53972d5c721fa1081"
date = "2025-09-17T19:53:46.980195Z (2d ago)"
variant = "full"

[system-info]
os = "macOS 15.6.1 (24G90)"
chip = "Apple M2 Pro"
total-cores = 12
memory = "32.00 GB"

[environment]
cwd = "/Users/USER"
cli-path = "/Users/USER"
os = "Mac"
shell-path = "/bin/zsh"
shell-version = "5.9"
terminal = "iTerm 2"
install-method = "brew"

[env-vars]
PATH = '/opt/homebrew/Cellar/pyenv-virtualenv/1.2.4/shims:/Users/USER/.pyenv/shims:/Users/USER/.pyenv/bin:/opt/homebrew/Cellar/pyenv-virtualenv/1.2.4/shims:/Users/USER/.pyenv/bin:/opt/homebrew/Cellar/pyenv-virtualenv/1.2.4/shims:/Users/USER/.pyenv/bin:/Users/USER/.pyenv/bin:/Users/USER/.toolbox/bin:/opt/homebrew/bin:/Users/USER/.cargo/bin:/opt/local/bin:/opt/local/sbin:/Library/Frameworks/Python.framework/Versions/2.7/bin:/Users/USER/.toolbox/bin:/workspace/USER/SourceCodeUtilities/src/Jackson-importer/perlModules/bin:/workspace/USER/SourceCodeUtilities/src/SourceCodeUtilities/configuration/bin:/apollo/env/SDETools/bin:/usr/local/bin:/usr/bin:/usr/sbin:/bin:/sbin:/usr/X11R6/bin:/usr/X11/bin:/usr/bin/mh:/Users/USER/bin:/usr/local/bin:/opt/local/bin:/opt/local/sbin:/System/Library/Frameworks/JavaVM.framework/Versions/1.6/Home/bin:/opt/homebrew/bin:/opt/homebrew/opt/macvim/bin:/Volumes/Workspaces/vs/SourceCodeUtilities/dev/src/SourceCodeUtilities/configuration/bin:/Users/USER/.local/bin:/Applications/Amazon\:Q.app/Contents/MacOS:/Users/USER/JCR/bin:/opt/app/oracle/product/9.2.0.3/bin:/usr/local/bin'
QTERM_SESSION_ID = "72821c5762054df18d77bc09315e0f10"
Q_SET_PARENT_CHECK = "1"
Q_TERM = "1.16.1"
SHELL = "/bin/tcsh"
TERM = "xterm-256color"
__CFBundleIdentifier = "com.googlecode.iterm2"
```