Remove unreachable dead code (#1176)

* Remove unreachable dead code

Delete symbols with no callers anywhere in the codebase, tests, or docs,
confirmed by a repo-wide search. These are internal/private or app-layer
(explorer) symbols, not part of the importable library's public API
(no __all__ / package re-export), so there is no user-facing change.

Removed:
- poc_runner.py: parse_import_csv_row (unused nested helper)
- change_management/version_storage.py: create_graph_snapshot_record
- context/graph_schema.py: drop_decision_schema
- explorer/dependencies.py: get_ws_manager (+ now-unused ConnectionManager import)
- explorer/routes/graph.py: _extract_node_embeddings (+ stale cross-ref comment)
- explorer/routes/ontology.py: ProposalState
- explorer/schemas.py: ErrorResponse, TemporalSnapshotResponse, ExportResponse,
  StandardMessageResponse
- semantic_extract/methods.py: _parse_entity_result, _parse_triplet_result
- triplet_store/methods.py: _get_query_engine (+ now-unused _global_query_engine)

Co-Authored-By: Vinv-AI <309466812+Vinv-AI@users.noreply.github.com>

* Address review: drop now-orphaned helper and fix stale docstring

- Remove _coerce_embedding_vector from explorer/routes/graph.py: its only
  non-recursive caller was _extract_node_embeddings (removed in this PR), so
  it is now dead. The live coercion logic lives in
  GraphSession._coerce_embedding_vector.
- Update explorer/dependencies.py module docstring: it no longer injects
  ConnectionManager (get_ws_manager was removed); note that websocket manager
  access is via app.state.ws_manager.

Co-Authored-By: Vinv-AI <309466812+Vinv-AI@users.noreply.github.com>

* Keep public helpers with a DeprecationWarning instead of removing them

create_graph_snapshot_record() and drop_decision_schema() are not
underscore-prefixed, so downstream users can import them directly from
their modules even though they are not re-exported from the package
__init__.py. A repo search only proves there are no in-tree callers.

Restore both unchanged and emit a DeprecationWarning on call, with a
matching ".. deprecated::" note in each docstring pointing at the
replacement. This keeps the PR non-breaking; the actual removal can
happen in a future major version.

The underscore-prefixed helper removals are unaffected.

---------

Co-authored-by: noQbot <noQbot@users.noreply.github.com>
Co-authored-by: Vinv-AI <309466812+Vinv-AI@users.noreply.github.com>
Co-authored-by: noQbot <anshul@vinv.ai>

poc_runner.py

@@ -187,15 +187,6 @@ def poc_vuln3():
             })
         return nodes
 
-    # Simulate the CSV parser — mirrors export_import.py lines 131-133
-    def parse_import_csv_row(row: dict) -> dict:
-        """Mirrors export_import.py CSV node ID extraction (no sanitization)."""
-        node_id = row.get("id") or row.get("node_id") or row.get(":ID") or row.get("_id")
-        return {
-            "id": str(node_id),  # ← UNSANITIZED
-            "type": row.get("type", "entity"),
-        }
-
     # Attack payloads
     payloads = [
         # Header injection payload (chained with VULN-1)