Address PR #3 review comments: fix error handling, remove dead code, add type annotations

[Copilot]

Addresses unresolved comments from PR #3 review and completes type annotations across all Python modules.

Error Handling

• All extraction phases (GraphQL, Releases, Commits, Workflows) now consistently set errors_occurred flag on failure
• Prevents incomplete data from being exported when any extraction phase fails

Code Cleanup

• Removed unused ATTR_TYPES constant in builder.py
• Removed dead code: _map_comments() function (defined but never called)

Documentation

Added explanatory comments for design decisions:

• Type conversion: OCEL 2.0 requires string values; type validation happens at schema level
• Timestamp handling: Object attributes use current time per OCEL 2.0 spec; UTC assumption for 'Z' suffix append
• N+1 pattern: fetch_commits_rest() documents acceptable performance tradeoff given API constraints

Type Annotations

• Completed return type annotations: main(), validate_ocel(), get_logger()
• Fixed duplicate Union import in validate_ocel.py

All modules now have complete type information for static analysis tools.

Original prompt

@copilot open a new pull request to apply changes based on the comments in this thread. Ignore the changes that have been already applied in main. Add type information to all the Python modules where no typing information is provided.

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