fix(ci): mypy override for optional perplexity client instead of inline ignore

CI has been red since 2026-06-17: the unofficial helallao perplexity client is
an optional local install absent in CI, so `import perplexity` raised
import-not-found there while the inline `type: ignore[import-untyped]` only
covered the installed-but-untyped local case — and any widened inline code
list trips unused-ignore on whichever side doesn't need it. A per-module
ignore_missing_imports override covers both environments.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: JuliaEdom

pyproject.toml

@@ -114,3 +114,9 @@ ignore_missing_imports = true
 [[tool.mypy.overrides]]
 module = ["plotly.*", "streamlit", "pandas", "pandas.*"]
 ignore_missing_imports = true
+
+# Unofficial Perplexity client (github.com/helallao/perplexity-ai): optional
+# local install, absent in CI — silence both import-untyped and import-not-found.
+[[tool.mypy.overrides]]
+module = ["perplexity"]
+ignore_missing_imports = true

src/nl_sql/llm/providers/helallao_perplexity.py

@@ -63,7 +63,7 @@ def __init__(
         if not model.strip():
             raise ProviderError("HelallaoPerplexityProvider requires non-empty model")
         try:
-            import perplexity as _pplx  # type: ignore[import-untyped]
+            import perplexity as _pplx
         except ImportError as e:
             raise ProviderError(
                 "helallao perplexity-ai not installed. Run: "