feat: resolve SPICE parametric expressions and sanitize numeric node names

Gap 12: Build a .param lookup table with multi-pass chained resolution so
parameter references (e.g. `.param tstep=1n` used in `.tran tstep ...`) and
brace expressions (`{Rval}`) resolve to concrete values during import.

Gap 23: Prefix `n` to digit-leading SPICE node names (e.g. `1` → `n1`) so
they form valid Cirq identifiers while preserving net identity.

Adds 6 new test cases covering param resolution, brace expressions,
chained params, and node name sanitization.

Author: cramt

cirq-frontend/src/lower.rs

@@ -3,10 +3,10 @@
 
 use cirq_ast::{
     AnalysisDecl, AnalysisItem, Argument, Attribute, BinOp, Circuit, CircuitItem, CodeDecl,
-    CoupledLineDecl, CoupledLineField, ElementInst, ExportDecl, Expr, FuncDecl, GlobalDecl,
-    IcDecl, IcEntry, Ident, Import, LetDecl, ModelDef, ModelParam, ModuleDef, ModuleInst,
-    OptionSetting, OptionsDecl, ParamDecl, PortDecl, PortDirection, QualifiedName, SaveDecl,
-    SaveTarget, SourceFile, TempDecl, TopLevel, UnaryOp, span::Span,
+    CoupledLineDecl, CoupledLineField, ElementInst, ExportDecl, Expr, FuncDecl, GlobalDecl, IcDecl,
+    IcEntry, Ident, Import, LetDecl, ModelDef, ModelParam, ModuleDef, ModuleInst, OptionSetting,
+    OptionsDecl, ParamDecl, PortDecl, PortDirection, QualifiedName, SaveDecl, SaveTarget,
+    SourceFile, TempDecl, TopLevel, UnaryOp, span::Span,
 };
 
 use crate::diagnostics::{Diagnostic, Severity};

cirq-frontend/src/resolve.rs

@@ -215,8 +215,7 @@ fn parse_and_extract_named(
     let items = parse_and_resolve(source, file_path, search_paths, visited, diags);
 
     let mut result = Vec::new();
-    let wanted: std::collections::HashSet<&str> =
-        names.iter().map(|n| n.name.as_str()).collect();
+    let wanted: std::collections::HashSet<&str> = names.iter().map(|n| n.name.as_str()).collect();
     let mut found: std::collections::HashSet<&str> = std::collections::HashSet::new();
 
     for item in &items {
@@ -537,14 +536,8 @@ mod tests {
                 _ => None,
             })
             .collect();
-        assert!(
-            model_names.contains(&"nch"),
-            "nch from export tt not found"
-        );
-        assert!(
-            model_names.contains(&"pch"),
-            "pch from export tt not found"
-        );
+        assert!(model_names.contains(&"nch"), "nch from export tt not found");
+        assert!(model_names.contains(&"pch"), "pch from export tt not found");
 
         // Should NOT have the bare model (not in any export).
         assert!(
@@ -687,8 +680,14 @@ mod tests {
             })
             .collect();
 
-        assert!(model_names.contains(&"nch_tt"), "tt export should be imported");
-        assert!(model_names.contains(&"nch_ff"), "ff export should be imported");
+        assert!(
+            model_names.contains(&"nch_tt"),
+            "tt export should be imported"
+        );
+        assert!(
+            model_names.contains(&"nch_ff"),
+            "ff export should be imported"
+        );
         assert!(
             !model_names.contains(&"nch_ss"),
             "ss export should NOT be imported"