docs(changelog): add entry for MCP server version fix (#870, closes #863)

CHANGELOG.md

@@ -11,6 +11,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- **MCP server reported a stale `0.4.0` version instead of the installed package version** (#870, closes #863) by @oiahoon
+  - `semantica/mcp_server/__init__.py` hardcoded `"version": "0.4.0"` in both the MCP `initialize` response (`SERVER_INFO`) and the `semantica://schema/info` resource, regardless of the actual installed `semantica` version — every MCP client (Claude Desktop, Windsurf, Cline, Continue, VS Code Copilot, etc.) showed the wrong server version. Both surfaces now derive from `semantica.__version__`, the package's authoritative version source, so they can no longer drift from `pyproject.toml`
+  - New regression coverage in `tests/test_mcp_server_version.py`, including `!= "0.4.0"` canaries and a cross-surface consistency check
+  - **Fixed along the way**: the separate root-level `mcp/` package (`mcp/__init__.py`, `mcp/server.py`, `mcp/resources/registry.py`) — a companion MCP server implementation not included in the built distribution, but documented in `mcp/__init__.py` as a supported way to run against Claude Desktop/Windsurf/etc. from a source checkout — had the same three hardcoded `0.4.0` literals; fixed the same way, with matching regression tests in `tests/test_mcp_package_version.py`
+
 - **`VectorStore._filter_by_metadata()` `AttributeError` on all persistent backends** (#857, closes #849) by @TaherTadpatri
   - `_filter_by_metadata()` iterated `self.metadata` directly, which only exists on the `inmemory` backend — any persistent backend (`faiss`, `qdrant`, `pinecone`, `milvus`, `pgvector`, `sqlite`, `weaviate`) crashed with `AttributeError` on `filter_decisions(query=None, ...)` / metadata-only filtering. Filtering is now delegated to a native `filter_by_metadata()` implemented on each backend store, using backend-native payload/SQL/JSON filtering (Qdrant `scroll()`, Pinecone `query()`, Milvus expression filters, PostgreSQL JSONB, SQLite `json_extract()`, Weaviate collection filters)
   - **Fixed along the way**: `PineconeStore.get_index()` and `filter_by_metadata()` called a nonexistent `self.describe_index_stats()` on the store itself (the method only exists on the `PineconeIndex` wrapper returned by `self.index`); the resulting `AttributeError` was silently swallowed, so dimension auto-detection always failed quietly. Now correctly calls `self.index.describe_index_stats()`