refactor: CheckFreshness and DiffDiagram take &str instead of &Path

crates/application/src/use_cases/check_freshness.rs

@@ -1,18 +1,17 @@
 use archlens_domain::{DomainError, NormalizedGraph, ports::DiagramRenderer};
 
-/// Compares the current rendered output against an on-disk file.
+/// Compares the current rendered output against provided file content.
 /// Returns `Ok(true)` if up to date, `Ok(false)` if stale.
 pub struct CheckFreshness<'a> {
     pub graph: &'a NormalizedGraph,
     pub renderer: &'a dyn DiagramRenderer,
-    pub existing_path: &'a std::path::Path,
+    pub existing_content: &'a str,
 }
 
 impl<'a> CheckFreshness<'a> {
     pub fn execute(&self) -> Result<bool, DomainError> {
         let rendered = self.renderer.render(self.graph.as_graph())?;
         let current = rendered.files().first().map(|f| f.content()).unwrap_or("");
-        let existing = std::fs::read_to_string(self.existing_path).unwrap_or_default();
-        Ok(current == existing)
+        Ok(current == self.existing_content)
     }
 }

crates/application/src/use_cases/diff_diagram.rs

@@ -12,22 +12,21 @@ impl DiffResult {
     }
 }
 
-/// Compares the rendered current graph against an existing diagram file and
+/// Compares the rendered current graph against provided diagram content and
 /// returns which lines were added or removed.
 pub struct DiffDiagram<'a> {
     pub graph: &'a NormalizedGraph,
     pub renderer: &'a dyn DiagramRenderer,
-    pub existing_path: &'a std::path::Path,
+    pub existing_content: &'a str,
 }
 
 impl<'a> DiffDiagram<'a> {
     pub fn execute(&self) -> Result<DiffResult, DomainError> {
         let rendered = self.renderer.render(self.graph.as_graph())?;
         let current = rendered.files().first().map(|f| f.content()).unwrap_or("");
-        let existing = std::fs::read_to_string(self.existing_path).unwrap_or_default();
 
         let current_lines: std::collections::HashSet<&str> = current.lines().collect();
-        let existing_lines: std::collections::HashSet<&str> = existing.lines().collect();
+        let existing_lines: std::collections::HashSet<&str> = self.existing_content.lines().collect();
 
         let added: Vec<String> = current_lines
             .difference(&existing_lines)