fix: harden task3 qdrant compatibility boundaries

harness/tht/ports/vector.py

@@ -45,6 +45,27 @@ class VectorStoreError(Exception):
     """Base error exposed by vector adapters."""
 
 
+class SemanticIndexIncompatibleError(VectorStoreError):
+    """The configured semantic collection cannot safely serve this workspace."""
+
+    code = "semantic_index_incompatible"
+
+    def __init__(self, message: str = "Qdrant semantic index is incompatible"):
+        super().__init__(f"{self.code}: {message}")
+
+
+class VectorTransportError(VectorStoreError):
+    """Qdrant could not be reached or returned an HTTP failure."""
+
+    def __init__(self, message: str, *, status_code: int | None = None):
+        super().__init__(message)
+        self.status_code = status_code
+
+
+class VectorResponseError(VectorStoreError):
+    """Qdrant returned a malformed response."""
+
+
 class VectorWriteUnavailable(VectorStoreError):
     """Raised when a deployment has no vector writer credential."""
 
@@ -86,13 +107,16 @@ class VectorStore(Protocol):
 
 
 __all__ = [
+    "SemanticIndexIncompatibleError",
     "VectorCapabilities",
     "VectorHealth",
     "VectorHit",
     "VectorReadUnavailable",
     "VectorRecord",
+    "VectorResponseError",
     "VectorStore",
     "VectorStoreError",
+    "VectorTransportError",
     "VectorWriteRecord",
     "VectorWriteUnavailable",
     "require_positive_limit",