chore(detach): update arg description & error messaging

[zwhitfield3]

Description

Work Item

This PR updates the model resource argument description to only specify an alias. In addition, this PR also updates the error messaging when an invalid alias is entered. This PR also fixes a regression from a previous refactor that used the incorrect model ID.

Testing

NOTE: Until the addon service name is updated to heroku-inference instead of inference, make sure you export the correct environment variable via export HEROKU_INFERENCE_ADDON="inference-dev"

1. Pull down branch & yarn && yarn build it up
2. Create a test app to detach the model attachment from via heroku apps:create test-cli-ai-plugin-app
3. Create a test model resource in preparation for creating a model attachment via heroku ai:models:create claude-3-5-haiku --as MY_EXAMPLE_MODEL --app test-cli-ai-plugin-app
4. Get the name of the addon name via heroku addons -a test-cli-ai-plugin-app. The name will be in parenthesis with the following format inference-dev-<adjective>-XXXXX
5. Create a model attachment via heroku addons:attach <inference-dev-<adjective>-XXXXX> -a test-cli-ai-plugin-app --as my_example_model_again
6. Confirm that using the addon name when detaching the model attachment errors and mentions needing a valid alias via ./bin/run ai:models:detach <inference-dev-<adjective>-XXXXX> -a test-cli-ai-plugin-app
7. Confirm that model attachment successfully detaches by using it's attachment alias via ./bin/run ai:models:detach my_example_model_again -a test-cli-ai-plugin-app

Test clean up

1. Destroy the model resource via heroku ai:models:destroy MY_EXAMPLE_MODEL -a test-cli-ai-plugin-app
2. Destroy the test app via heroku apps:destroy -a test-cli-ai-plugin-app

[leoncalermo]

LGTM!!