refactor: use Mapping[str, str] for read-only base_sources parameter #858
Description
Summary
The SemanticAnalyzer protocol and all implementations accept base_sources: dict[str, str] but never mutate it. Using Mapping[str, str] would express the read-only contract at the type level.
Finding source
Pre-PR review agents (type-design-analyzer) flagged this during #611 review.
Scope
- Change
base_sourcesparameter type fromdict[str, str]toMapping[str, str]in:SemanticAnalyzerprotocolAstSemanticAnalyzer.analyzeLlmSemanticAnalyzer.analyzeCompositeSemanticAnalyzer.analyze- All four check functions in
semantic_checks.py
- Add
from collections.abc import Mappingimports