fix(ingest): materialize single-file PLC uploads so the scanner finds them

A PlcProject uploaded as a single .st/.xml file (not a zip) was stored as a
content-addressed blob with no extension, so the PLC scanner's extension-based
file discovery skipped it — an uploaded project produced zero findings.

When an "extractable" blob turns out not to be an archive, materialize it into
the artifact work dir under its original file name (from source_ref, which the
upload handler sets to the uploaded filename). analyze_tree then discovers it by
extension and reports a readable path. Falls back to the raw blob if the copy
fails. Covers the demo's upload -> scan path end to end.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

compliance-agent/src/ingest/mod.rs

@@ -162,14 +162,27 @@ fn ingest_blob(
         match blob::extract_zip(&stored, &dest) {
             Ok(()) => dest,
             Err(e) => {
-                // Not a zip (e.g. a tar.gz source archive) — keep the blob and
+                // Not a zip container — this is a single uploaded file (e.g. a
-                // note it so later stages can decide what to do.
+                // `.st`/`.xml` PLC project or a `.tar.gz`). The content-addressed
+                // blob has no extension, so materialize it into a working dir
+                // under its original name; extension-based scanners (PLC) can then
+                // discover it and report a readable path.
                 facts.push(DetectedFact::new(
                     "archive_unextracted",
                     e.to_string(),
                     "ingest",
                 ));
-                stored.clone()
+                match materialize_single(&stored, &dest, &blob_file_name(artifact)) {
+                    Ok(dir) => dir,
+                    Err(copy_err) => {
+                        facts.push(DetectedFact::new(
+                            "materialize_failed",
+                            copy_err.to_string(),
+                            "ingest",
+                        ));
+                        stored.clone()
+                    }
+                }
             }
         }
     } else {
@@ -186,6 +199,27 @@ fn ingest_blob(
     })
 }
 
+/// Copy a stored blob into `dest`/`name`, returning `dest`. Used when an
+/// "extractable" artifact turns out to be a single file rather than an archive.
+fn materialize_single(stored: &Path, dest: &Path, name: &str) -> Result<PathBuf, AgentError> {
+    std::fs::create_dir_all(dest)?;
+    std::fs::copy(stored, dest.join(name))?;
+    Ok(dest.to_path_buf())
+}
+
+/// A safe, single-segment file name for an artifact, preserving the original
+/// extension so scanners can identify it. Derives from `source_ref` (the
+/// uploaded/original file name); `file_name` strips any directory components,
+/// so this is traversal-safe. Falls back to the artifact id.
+fn blob_file_name(artifact: &Artifact) -> String {
+    Path::new(&artifact.source_ref)
+        .file_name()
+        .and_then(|n| n.to_str())
+        .map(str::to_string)
+        .filter(|s| !s.is_empty())
+        .unwrap_or_else(|| format!("artifact-{}", artifact.id))
+}
+
 /// An artifact with no on-disk form: record a single fact, no hash/path.
 fn metadata_only(artifact: &Artifact, fact: DetectedFact) -> IngestedArtifact {
     IngestedArtifact {
@@ -331,4 +365,52 @@ mod tests {
         assert_eq!(creds.ssh_key_path.as_deref(), Some("/default/ssh/key"));
         assert!(creds.auth_token.is_none());
     }
+
+    /// A single uploaded PLC file (not an archive) must land in a working dir
+    /// under its original name so the PLC scanner can discover it by extension
+    /// and report a readable path — the demo's upload → scan path.
+    #[test]
+    fn single_uploaded_plc_file_is_materialized_and_scannable() {
+        use compliance_core::models::PlcFormat;
+
+        let scratch = Scratch::new();
+        let store = scratch.0.join("store");
+        // Simulate the upload handler: bytes written to an `uploads/` path,
+        // `source_ref` carrying the original (clean) file name.
+        let uploads = scratch.0.join("uploads");
+        std::fs::create_dir_all(&uploads).expect("mkdir uploads");
+        let uploaded = uploads.join("a1b2c3_pump_station.st");
+        std::fs::write(
+            &uploaded,
+            "PROGRAM P\nVAR\n  ApiKey : STRING := 'sk-live-1234';\nEND_VAR\nEND_PROGRAM\n",
+        )
+        .expect("write st");
+
+        let mut artifact = Artifact::plc_project("pump_station.st", PlcFormat::StructuredText);
+        artifact.stored_path = Some(uploaded.to_string_lossy().to_string());
+
+        let ctx = ctx_for(&store, "t-plc");
+        let out = ingest_artifact(&artifact, &ctx).expect("ingest");
+
+        // Working path is a directory (not the extensionless blob) holding the
+        // file under its original name.
+        let wp = out.working_path.expect("working path");
+        assert!(wp.is_dir(), "expected a working dir, got {wp:?}");
+        assert!(wp.join("pump_station.st").is_file());
+
+        // The PLC scanner finds the hardcoded credential and reports a clean path.
+        let findings = crate::pipeline::plc::analyze_tree(&wp, "t-plc");
+        assert!(
+            !findings.is_empty(),
+            "scanner should flag the uploaded file"
+        );
+        assert!(findings
+            .iter()
+            .any(|f| f.rule_id.as_deref() == Some("plc-hardcoded-credential")));
+        assert_eq!(
+            findings[0].file_path.as_deref(),
+            Some("pump_station.st"),
+            "finding should reference the original file name"
+        );
+    }
 }