Repair rule: conservative TypeError guards

[guohuancui123-a11y]

Goal

Explore conservative repair rules for selected TypeError runtime failures.

Why

TypeError is common in Python apps, but many cases are too broad to repair safely. RepairLoop should only handle narrow patterns where a minimal local fix is obvious and verifiable.

Candidate patterns

• Missing required positional argument in a local demo-style call.
• Unexpected None where a default empty value is safe in a clearly local example.
• String/path coercion issues where str() or Path() is an obvious narrow fix.

Acceptance criteria

• Start with one narrow TypeError pattern only.
• Unknown or ambiguous TypeError cases produce guidance, not patches.
• Tests include both supported and unsupported examples.
• The applied fix must be verified by rerunning the original command.

Safety notes

Do not add broad AI-style rewrites. The first rule should be intentionally small, explainable, and easy to reject when uncertain.