fix: handle missing slug in create-report command

[sentry]

This PR addresses an issue where the create-report command would crash with a ValueError: The provided slug is invalid if the slug argument was None.

The root cause was that encode_slug (called by create_report_logic) does not accept None as a valid slug. The slug could be None if it was not explicitly provided via the --slug CLI option and could not be auto-detected by the CI adapter (e.g., when running in a non-CI local environment).

The fix introduces a check at the beginning of create_report_logic to explicitly verify if slug is None. If it is, a click.ClickException is raised with a user-friendly message, guiding the user to either provide the --slug option or ensure their CI environment is correctly configured. This prevents the unhandled ValueError and provides a clearer error experience.

Fixes CLI-GZ

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[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
723	1	722	1

View the full list of 1 ❄️ flaky test(s)

api.temp.calculator.test_calculator::test_divide

Flake rate in main: 100.00% (Passed 0 times, Failed 1726 times)

Stack Traces | 0.001s run time

def
                test_divide():
                > assert Calculator.divide(1, 2) == 0.5
                E assert 1.0 == 0.5
                E + where 1.0 = <function Calculator.divide at 0x104c9eb90>(1, 2)
                E + where <function Calculator.divide at 0x104c9eb90> = Calculator.divide
                .../temp/calculator/test_calculator.py:30: AssertionError

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