refactor: replace AssertionError with ValueError

[mkoura]

Replaces all instances of raising AssertionError with ValueError for invalid argument or state errors across the codebase. This improves clarity and aligns with Python's standard exception usage for value validation. FileNotFoundError is used where appropriate for missing files. No functional changes to logic or error messages.

[Copilot]

Pull Request Overview

This PR improves error handling by replacing AssertionError with more semantically appropriate exception types for input validation scenarios.

• Replaces AssertionError with ValueError for input validation errors across all modules
• Replaces AssertionError with FileNotFoundError for a file existence check in clusterlib_helpers.py

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
cardano_clusterlib/txtools.py	Updated 4 input validation errors to raise ValueError instead of AssertionError
cardano_clusterlib/transaction_group.py	Updated 11 parameter validation errors to raise ValueError instead of AssertionError
cardano_clusterlib/stake_pool_group.py	Updated 1 parameter validation error to raise ValueError instead of AssertionError
cardano_clusterlib/stake_address_group.py	Updated 6 parameter validation errors to raise ValueError instead of AssertionError
cardano_clusterlib/query_group.py	Updated 2 parameter validation errors to raise ValueError instead of AssertionError
cardano_clusterlib/gov_vote_group.py	Updated 4 parameter validation errors to raise ValueError instead of AssertionError
cardano_clusterlib/gov_group.py	Updated 1 parameter validation error to raise ValueError instead of AssertionError
cardano_clusterlib/gov_drep_group.py	Updated 3 parameter validation errors to raise ValueError instead of AssertionError
cardano_clusterlib/gov_committee_group.py	Updated 3 parameter validation errors to raise ValueError instead of AssertionError
cardano_clusterlib/gov_action_group.py	Updated 4 parameter validation errors to raise ValueError instead of AssertionError
cardano_clusterlib/clusterlib_helpers.py	Updated file existence check to raise FileNotFoundError instead of AssertionError
cardano_clusterlib/address_group.py	Updated 2 parameter validation errors to raise ValueError instead of AssertionError

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