Support loading prompt from yml file

[sgoedecke]

Supports loading prompt from a yml file via the --file parameter.

[Copilot]

Pull Request Overview

Adds the ability to load a prompt definition from a YAML file via the --file flag, preload its messages and parameters, and include a test verifying basic YAML loading.

• Introduce s.prompt.yml as an example prompt definition.
• Parse .prompt.yml into a promptFile struct in run.go and inject its data before executing the command.
• Add a test in run_test.go to confirm that YAML-loaded messages and temperature are applied.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
s.prompt.yml	New example YAML file defining prompt metadata.
cmd/run/run.go	Parse --file flag, unmarshal YAML, preload messages and parameters.
cmd/run/run_test.go	Test that --file loads YAML and applies its settings.

Comments suppressed due to low confidence (1)

cmd/run/run_test.go:85

• There is no test verifying that a CLI flag overrides a value from the YAML file. Add a case where you pass --temperature alongside --file and assert that the flag value takes effect.

t.Run("--file pre-loads YAML and CLI overrides take precedence", func(t *testing.T) {

[cheshire137]

That _, is that an error? Should you maybe check it and return early if it's non-nil?

[sgoedecke]

Yeah, it's probably wise to do that, but I think it's safe to follow up in a later change. The possible errors here are things like "you defined the file flag as an integer but are trying to GetString it", not really things that users could trigger.