Improve clarity of model run command's error message

[garman]

closes: github/models#322

Adds more detail to the error output when a given model name is either empty or otherwise not found.

---

Before (taken from issue):

$ gh models run ThisDoesNotExist Mary had a little lamb
Error: bad request
{"error":{"code":"unknown_model","message":"Unknown model: thisdoesnotexist","details":null}}

Usage:
  gh run [model] [prompt] [flags]

Flags:
  -h, --help                   help for run
      --max-tokens string      Limit the maximum tokens for the model response.
      --system-prompt string   Prompt the system.
      --temperature string     Controls randomness in the response, use lower to be more deterministic.
      --top-p string           Controls text diversity by selecting the most probable words until a set probability is reached.

---

After:

danielgarman:Daniel’s MacBook Pro
╰─\gh-models:models/322-improve-error-messaging-root*:% ./gh-models run "" "mary had a little lamb"
Error: The specified model name is not found. Run 'gh models list' to see available models or 'gh models run' to select interactively.
Usage:
  gh run [model] [prompt] [flags]

Flags:
  -h, --help                   help for run
      --max-tokens string      Limit the maximum tokens for the model response.
      --system-prompt string   Prompt the system.
      --temperature string     Controls randomness in the response, use lower to be more deterministic.
      --top-p string           Controls text diversity by selecting the most probable words until a set probability is reached.

danielgarman:Daniel’s MacBook Pro
╰─\gh-models:models/322-improve-error-messaging-root*:% ./gh-models run "asdfasdf" "mary had a little lamb"
Error: The specified model name is not found. Run 'gh models list' to see available models or 'gh models run' to select interactively.
Usage:
  gh run [model] [prompt] [flags]

Flags:
  -h, --help                   help for run
      --max-tokens string      Limit the maximum tokens for the model response.
      --system-prompt string   Prompt the system.
      --temperature string     Controls randomness in the response, use lower to be more deterministic.
      --top-p string           Controls text diversity by selecting the most probable words until a set probability is reached.

or

danielgarman:Daniel’s MacBook Pro
╰─\gh-models:models/322-improve-error-messaging-root:% ./gh-models run foo "hello world"
Error: The specified model name is not found. Run 'gh models list' to see available models or 'gh models run' to select interactively.
Usage:
  gh run [model] [prompt] [flags]

Flags:
  -h, --help                   help for run
      --max-tokens string      Limit the maximum tokens for the model response.
      --system-prompt string   Prompt the system.
      --temperature string     Controls randomness in the response, use lower to be more deterministic.
      --top-p string           Controls text diversity by selecting the most probable words until a set probability is reached.

[cheshire137]

Looks reasonable to me! Can you verify that the new error message comes up if you try gh models run foo "hello world"?

[cheshire137]

Could include the value that was given, like "The specified model name 'foo'".

[garman]

Can you verify that the new error message comes up if you try gh models run foo "hello world"?

Yep!

danielgarman:Daniel’s MacBook Pro
╰─\gh-models:models/322-improve-error-messaging-root:% ./gh-models run foo "hello world"
Error: The specified model name is not found. Run 'gh models list' to see available models or 'gh models run' to select interactively.
Usage:
  gh run [model] [prompt] [flags]

Flags:
  -h, --help                   help for run
      --max-tokens string      Limit the maximum tokens for the model response.
      --system-prompt string   Prompt the system.
      --temperature string     Controls randomness in the response, use lower to be more deterministic.
      --top-p string           Controls text diversity by selecting the most probable words until a set probability is reached.