chore(source): scope private policy observer and remove redundant import

crates/oa-core/src/language/analysis_source/budget.rs

@@ -221,6 +221,7 @@ impl Budget {
         Ok(value)
     }
     /// Immutable exact policy snapshot for private deliberate-snapshot continuation.
+    #[cfg(test)]
     pub(super) fn limits(&self) -> Limits {
         self.limits
     }

crates/oa-core/tests/mixed_source8_read.rs

@@ -2,7 +2,7 @@
 //! Expected models use authored public values, never a parser or formatter oracle.
 use oa_core::analysis as a;
 use oa_core::analysis_numeric::Exact;
-use oa_core::language::{self, ParseLimits, Span};
+use oa_core::language::{ParseLimits, Span};
 use oa_core::source_project::{ProjectLimits, SourceBundle, SourceDiagnostic};
 pub use oa_core::*;
 use std::collections::BTreeMap;