fix: resolve check command source path from repo root (#120)

The check command resolved the header's source path relative to the
pipeline YAML's parent directory. Since the header stores paths relative
to the repository root (e.g. \�gents/ctf.md\), this doubled the
directory prefix when the pipeline lived in a subdirectory
(\�gents/agents/ctf.md\).

Walk up from the pipeline file to find the .git directory and use that
as the base for resolving the source path.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jamesadevine

src/compile/mod.rs

@@ -209,11 +209,23 @@ pub async fn check_pipeline(pipeline_path: &str) -> Result<()> {
             )
         })?;
 
-    // Resolve source path relative to the pipeline file's parent directory
-    let source_path = pipeline_path
-        .parent()
-        .unwrap_or_else(|| Path::new("."))
-        .join(&header_meta.source);
+    // The header stores the source path relative to the repository root.
+    // Walk up from the pipeline file to find the .git directory, then resolve
+    // the source path relative to that root.
+    let pipeline_abs = if pipeline_path.is_absolute() {
+        pipeline_path.to_path_buf()
+    } else {
+        std::env::current_dir()
+            .unwrap_or_else(|_| PathBuf::from("."))
+            .join(pipeline_path)
+    };
+    let repo_root = find_repo_root(&pipeline_abs).with_context(|| {
+        format!(
+            "Could not find repository root (no .git directory) from {}",
+            pipeline_path.display()
+        )
+    })?;
+    let source_path = repo_root.join(&header_meta.source);
 
     info!(
         "Checking pipeline integrity: {} -> {} (source from header)",
@@ -266,6 +278,19 @@ pub async fn check_pipeline(pipeline_path: &str) -> Result<()> {
     Ok(())
 }
 
+/// Walk up from `start` to find the nearest directory containing `.git`.
+fn find_repo_root(start: &Path) -> Option<PathBuf> {
+    let mut current = start.to_path_buf();
+    loop {
+        if current.join(".git").exists() {
+            return Some(current);
+        }
+        if !current.pop() {
+            return None;
+        }
+    }
+}
+
 /// Normalize a string by removing all whitespace characters.
 ///
 /// Used for integrity checks so that formatting-only differences