feat(vector): add Valkey Search vector database backend (#2276)

* feat(vector): add Valkey Search vector database backend

Add a new opt-in VectorDatabase backend backed by the Valkey Search module
(valkey/valkey-bundle), accessed via the official valkey-glide client's native
ft command namespace.

- Implements the full VectorDatabase ABC: VECTOR, FULL_TEXT and HYBRID search,
  all 8 metadata filter operators, and pagination with exact totals.
- HYBRID uses filter-then-KNN (no app-side weighted fusion); vector_weight is
  accepted for interface parity but NOT honored (docstring + one-time warning +
  docs caveat).
- Lazy connect so a down Valkey never blocks boot; mandatory
  client_name=langbot_vector_client; optional auth + TLS (never logged).
- Registered via a single elif branch in vector/mgr.py; disabled by default
  (vdb.use stays chroma) for toC compatibility.
- Adds valkey-glide>=2.4.1,<3.0.0; no protobuf/pydantic downgrade; no ORM
  change so no Alembic migration.
- Unit tests (fast lane, no server) + slow-gated integration tests
  (TEST_VALKEY_URL, valkey/valkey-bundle:9.1.0) + integration doc.

* fix(vector): paginate Valkey Search deletes and guard delete_by_filter

Address self-review follow-ups for the Valkey Search VDB backend:

- _search_keys now paginates through the full result set in batches of
  _DELETE_SCAN_BATCH instead of capping at a single hard-coded 10000-key
  page, so delete_by_file_id / delete_by_filter fully remove files and
  filters that match more than one page of chunks (no orphaned vectors).
- Add unit regression tests for the delete_by_filter mass-deletion guard:
  a filter referencing only non-indexed fields must skip and return 0
  (never fall back to match-all), and a supported filter still deletes
  matching keys.

* refactor(vector): harden Valkey Search backend and add adversarial tests

Address the self-review NICE-TO-HAVE items for the Valkey Search VDB backend:
- Guard the username-without-password credential edge (skip auth + warn
  instead of building ServerCredentials(password=None, ...), which glide
  rejects).
- Add an async close() teardown that closes the glide client and resets
  cached state (re-init is safe via the existing None guard).
- Hoist 'import json' to module top (was imported inside three methods).
- Document the FT TAG literal-brace limitation in _escape_tag (fails closed,
  never widens).

Tests:
- Add an adversarial-input integration test proving crafted file_id /
  query_text cannot break out of or widen a query (fail-closed on braces).
- Add unit tests for close() and the credential-build guard.

Signed-off-by: Daria Korenieva <daric2612@gmail.com>

* fix(vector): make Valkey Search file_id TAG support arbitrary characters

Valkey Search's FT TAG query parser cannot handle '{', '}' or '*' even when
backslash-escaped, so a file_id containing those characters previously
produced an unparseable query (it failed closed / raised). Percent-encode
exactly those FT-unsafe characters (plus '%' for reversibility) in the
file_id TAG value, applied identically at write time and query time, so an
arbitrary file_id round-trips. For normal UUID/hash ids this is a no-op and
the stored value is unchanged; the original file_id is always preserved
verbatim in metadata_json.

Strengthen the adversarial integration test to assert a brace/star-bearing
file_id matches and deletes exactly its own row (no widening, no raise), and
add unit tests for _encode_file_id and the filter encoding.

Signed-off-by: Daria Korenieva <daric2612@gmail.com>

* refactor(vector): address Valkey Search review feedback

- Add configurable request_timeout (default 5000ms; glide default 250ms is
  too low for KNN); expose in config.yaml + docs table
- Validate embedding dimension consistency in add_embeddings (fail fast on
  mixed lengths to avoid silent KNN corruption)
- Use ft.info (O(1)) instead of ft.list (O(n)) for index existence checks in
  the query hot path; also closes the check-then-create TOCTOU window
- Pipeline HSETs via a non-atomic Batch instead of N sequential awaits
- Extract shared _iter_reply_docs to deduplicate reply parsing between
  _reply_to_chroma and list_by_filter
- Parenthesize multi-condition pre-filters before the => KNN clause
- Fail closed when a username is configured without a password
- Catch only RequestError on ft.dropindex (let connection/auth errors surface)
- Bound the delete_collection SCAN loop with a safety cap
- Add VectorDatabase.close() (no-op default) + VectorDBManager.shutdown()
- Simplify _MATCH_ALL literal; normalize typing to builtin generics

* fix(vector/valkey_search): address round-2 review feedback

- Serialize lazy client creation with an asyncio.Lock (double-checked) so
  concurrent first-use callers don't construct and leak duplicate clients.
- Make the filter operator chain exhaustive: raise on an unhandled op rather
  than silently dropping the condition (which could widen delete_by_filter).
- Cast numeric range (///) values to float, failing closed on
  non-numeric input and pre-empting a future NUMERIC-field injection surface.

* refactor(vector): remove shutdown/close from base ABC per maintainer feedback Per maintainer request, interface changes to VectorDatabase ABC and VectorDBManager should be in a separate PR with implementation across all backends. The ValkeySearchVectorDatabase.close() method remains but does not override an ABC method.

Signed-off-by: Daria Korenieva <daric2612@gmail.com>

* docs(test): list valkey_search in vdb coverage exclusions Add valkey_search to the documented vector/vdbs/ coverage-exclusion list, matching the existing chroma/milvus/pgvector/qdrant/seekdb entries. These adapters require a live database instance and are covered by env-gated integration tests instead of unit tests.

Signed-off-by: Daria Korenieva <daric2612@gmail.com>

---------

Signed-off-by: Daria Korenieva <daric2612@gmail.com>

tests/unit_tests/vector/test_mgr.py

@@ -33,7 +33,7 @@ class TestVectorDBManagerInitialization:
         mocks['langbot.pkg.core.app'] = MagicMock()
 
         # Mock all VDB backend implementations
-        for backend in ['chroma', 'qdrant', 'seekdb', 'milvus', 'pgvector_db']:
+        for backend in ['chroma', 'qdrant', 'seekdb', 'milvus', 'pgvector_db', 'valkey_search']:
             mocks[f'langbot.pkg.vector.vdbs.{backend}'] = MagicMock()
 
         return mocks
@@ -123,6 +123,25 @@ class TestVectorDBManagerInitialization:
 
             mock_seekdb_class.assert_called_once_with(mock_app)
 
+    def test_initialize_valkey_search_backend(self):
+        """Valkey Search config uses ValkeySearchVectorDatabase backend."""
+        vdb_config = {'use': 'valkey_search'}
+        mock_app = self._create_mock_app(vdb_config)
+
+        mocks = self._make_vector_import_mocks()
+        mock_valkey_class = MagicMock()
+        mocks['langbot.pkg.vector.vdbs.valkey_search'].ValkeySearchVectorDatabase = mock_valkey_class
+
+        with isolated_sys_modules(mocks):
+            from langbot.pkg.vector.mgr import VectorDBManager
+
+            mgr = VectorDBManager(mock_app)
+
+            import asyncio
+            asyncio.get_event_loop().run_until_complete(mgr.initialize())
+
+            mock_valkey_class.assert_called_once_with(mock_app)
+
     def test_initialize_milvus_backend_with_uri(self):
         """Milvus config with custom URI."""
         vdb_config = {