fix: guard against closed streams in promo and missing vector tables (#579, #607)

- Wrap isatty() in _is_interactive_session() with try/except ValueError
  so MCP stdio transport shutdown no longer produces noisy tracebacks
- Check both search_vector_chunks AND search_vector_embeddings exist
  before running JOIN queries in get_embedding_status(), fixing
  OperationalError when only the chunks table is present
- Add test for closed-stream scenario

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: phernandez <paul@basicmachines.co>

src/basic_memory/cli/promo.py

@@ -24,7 +24,13 @@ def _promos_disabled_by_env() -> bool:
 
 def _is_interactive_session() -> bool:
     """Return whether stdin/stdout are interactive terminals."""
-    return sys.stdin.isatty() and sys.stdout.isatty()
+    try:
+        return sys.stdin.isatty() and sys.stdout.isatty()
+    except ValueError:
+        # Trigger: stdin/stdout already closed (e.g., MCP stdio transport shutdown)
+        # Why: isatty() raises ValueError on closed file descriptors
+        # Outcome: treat as non-interactive, suppressing promo output
+        return False
 
 
 def _build_cloud_promo_message() -> str: