Recognize match pattern captures as assignments

[yangfan-yf-yf]

Description

Pattern capture names on MatchAs, MatchStar, and MatchMapping are string fields, so the scope visitor did not register them as assignments. Rename consequently rejected those names as unresolved. Inline could also replace a capture with a value pattern, changing program semantics.

This registers the three capture forms in their enclosing scope, returns a conservative unknown inference result for pattern assignments, and rejects inline whenever the selected name has a pattern-capture assignment. Rename now updates both capture definitions and references.

Fixes #861

Checklist

• I have added tests that prove the fix is effective
• I have updated CHANGELOG.md

Validation

• Full suite: 2121 passed, 12 skipped, 5 xfailed
• Relevant selection: 442 passed, 10 skipped
• All configured pre-commit checks for the changed Python files pass
• git diff origin/master...HEAD --check passes