Credentials - Local credential script tries to look up cached credentials.

[sangee2004]

gptscript version v0.0.0-dev-f4284f43-dirty

Steps to reproduce the problem:

1. Execute the following gptscript with a tool that has a credential with name - slack-message-credential-tool defined locally in it.

Tools: github.com/sangee2004/slack-message

Send a message to "sangeetest" channel saying "hello from gptscript".

2. User is prompted to enter the credentials as part of this script execution.
   At this time , the following credential gets cached

gptscript credential --all-contexts
CONTEXT   TOOL
default   slack-message-credential-tool

3. Now execute the following script which has a local credential with name - slack-message-credential-tool

credential: slack-message-credential-tool
Tools: github.com/gptscript-ai/slack-message

Send a message to "sangeetest" channel saying "hello from gptscript".

---
name: slack-message-credential-tool

#!/usr/bin/env bash

output=$(gptscript -q --disable-cache sys.prompt '{"message":"Please enter your slack credential.","fields":"credential","sensitive":"true"}')
credential=$(echo $output | jq -r '.credential')
echo "{\"env\":{\"\GPTSCRIPT_SLACK_TOKEN":\"$credential\"}}"

This results in trying to serve the credentials from cached entry ( it fails right now because of #237).

Expected Behavior:
We do not expect credentials from cached entry to be used in this case and user should be prompted to enter credentials.

[sangee2004]

Tested with gptscript version v0.0.0-dev-656ae77b-dirty

When testing the steps mentioned in the issue , there is no credential entry stored for the the credentials after step 1.

Able to run the gptscript from step 3 successfully. I am prompted to enter credentials as expected.