Fix baseUrl reassignment error when trimming trailing slash

[ZimperiumBrian]

Problem

When console_url ends with a trailing slash, the action attempts to normalize it by trimming the slash.

However, baseUrl is currently declared as const, which causes a runtime crash when reassignment is attempted.

Evidence

GitHub Actions runtime error:

TypeError: Assignment to constant variable.
at dist/index.js:44471

Fix

Change const baseUrl to let baseUrl so trailing-slash normalization works correctly.

Impact

Prevents the action from crashing when users configure console_url with a trailing slash.
This aligns with the existing normalization logic already present in the code.

[exlegalalien]

Will fix in a separate branch/PR