The `copilot_model` variable was restricted to a hardcoded enum of three
models (`claude-sonnet-4`, `claude-sonnet-4.5`, `gpt-5`). Models change
fast and this validation was blocking users from using newer models.
## Changes
- Remove `validation` block from `copilot_model` variable in `main.tf`
- Update variable description to indicate any Copilot-supported model
can be used
- Replace enum validation test with a test that verifies arbitrary model
strings are accepted
- Bump module version to `0.4.1` in README examples
Closes#832
> 🤖 This PR was created with the help of Coder Agents, and needs a human
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