Systematically identify and fix all failing tests using smart error grouping.

• Groups failures by error type, affected module, and root cause, then prioritizes fixes by impact and dependency order
• Fixes infrastructure issues first (imports, dependencies, configuration), followed by API changes, then logic bugs
• Runs focused test subsets after each fix using pytest markers and file patterns to verify progress before moving to the next group
• Follows a structured workflow: initial test run, error analysis, grouped fixing with verification, and final full-suite validation