H1+M2 review findings: CSV 5000x50 render cap (truncated with note) + stale output sweep; 4 regression tests (H1x3, M2x1); USER_GUIDE truncation docs

app.py

@@ -67,6 +67,7 @@ WORKER_SLOTS = threading.BoundedSemaphore(4)
 
 # Crash leftovers: sweep work dirs / uploads older than these at startup.
 STALE_WORK_SECONDS = 6 * 3600
+STALE_OUTPUT_SECONDS = 6 * 3600
 STALE_UPLOAD_SECONDS = 3600
 
 app = Flask(__name__)
@@ -374,8 +375,32 @@ def _sweep_stale_work_dirs() -> None:
             pass
 
 
+def _sweep_stale_output_files() -> None:
+    """Remove OUTPUT_DIR files left by crashed runs older than the 6h window.
+
+    Symmetric to _sweep_stale_work_dirs (finding M2: stale output sweep). Only
+    finished output files are removed (the directory is dedicated to generated
+    PDFs); files inside the window are left untouched.
+    """
+    now = time.time()
+    try:
+        entries = list(OUTPUT_DIR.iterdir())
+    except OSError:
+        return
+    for entry in entries:
+        if not entry.is_file():
+            continue
+        try:
+            if now - entry.stat().st_mtime > STALE_OUTPUT_SECONDS:
+                entry.unlink(missing_ok=True)
+        except OSError:
+            pass
+
+
 # Crash leftovers from the previous process start (finding: stale work dirs).
 _sweep_stale_work_dirs()
+# Stale generated outputs from the previous process start (finding M2).
+_sweep_stale_output_files()
 
 
 # --------------------------------------------------------------------------