Add frontmatter example to role check error message

[Copilot]

When workflows fail permission checks, users receive an error message but no guidance on how to fix it in the workflow frontmatter.

Changes

• Enhanced error message in check_membership.cjs: Added inline example showing how to configure the roles field in frontmatter with the user's actual permission level
• Updated test expectations: Modified test to validate the new message format includes the example

Example

Before:

Access denied: User 'contributor' is not authorized. Required permissions: admin, write

After:

Access denied: User 'contributor' is not authorized. Required permissions: admin, write. 
To allow this user to run the workflow, add their role to the frontmatter. 
Example: roles: [admin, write, read]

The example dynamically includes the user's actual permission level (read in this case) alongside the currently required permissions, making it immediately actionable.

Original prompt

Update the role check message in JavaScript (when a workflow does not run because role is not supported), to provide an example on how to fix the issue in the front matter

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