feat: Enhance Vector Stores config with full configurations (#4397)

# What does this PR do?

Enhances the Vector Stores config with full set of appropriate
configurations
- Add FileIngestionParams, ChunkRetrievalParams, and FileBatchParams
subconfigs
- Update RAG memory, OpenAI vector store mixin, and vector store utils
to use configuration
  - Fix import organization across vector store components
  - Add comprehensive vector stores configuration documentation
  - Update docs navigation to include vector store configuration guide
- Delete `memory/constants.py` and move constant values directly into
Pydantic models

## Test Plan
Tests updated + CI

---------

Signed-off-by: Francisco Javier Arceo <farceo@redhat.com>

tests/unit/core/routers/test_vector_io.py

@@ -156,7 +156,6 @@ async def test_query_rewrite_functionality():
     from unittest.mock import MagicMock
 
     from llama_stack.core.datatypes import QualifiedModel, RewriteQueryParams, VectorStoresConfig
-    from llama_stack.providers.utils.memory.constants import DEFAULT_QUERY_REWRITE_PROMPT
     from llama_stack_api import VectorStoreSearchResponsePage
 
     mock_routing_table = Mock()
@@ -197,7 +196,7 @@ async def test_query_rewrite_functionality():
 
     # Verify default prompt is used
     prompt_text = chat_call_args.messages[0].content
-    expected_prompt = DEFAULT_QUERY_REWRITE_PROMPT.format(query="test query")
+    expected_prompt = "Expand this query with relevant synonyms and related terms. Return only the improved query, no explanations:\n\ntest query\n\nImproved query:"
     assert prompt_text == expected_prompt
 
     # Verify routing table was called with rewritten query and rewrite_query=False

tests/unit/core/test_vector_stores_config.py

@@ -110,22 +110,23 @@ class TestOptionalArchitecture:
         assert config.annotation_prompt_params is not None
         assert "{num_chunks}" in config.file_search_params.header_template
 
-    def test_guaranteed_defaults_match_constants(self):
-        """Test that guaranteed defaults match expected constant values."""
-        from llama_stack.providers.utils.memory.constants import (
-            DEFAULT_CONTEXT_TEMPLATE,
-            DEFAULT_FILE_SEARCH_HEADER_TEMPLATE,
-        )
-
+    def test_guaranteed_defaults_have_expected_values(self):
+        """Test that guaranteed defaults have expected hardcoded values."""
         # Create config with guaranteed defaults
         config = VectorStoresConfig()
 
-        # Verify defaults match constants
+        # Verify defaults have expected values
         header_template = config.file_search_params.header_template
         context_template = config.context_prompt_params.context_template
 
-        assert header_template == DEFAULT_FILE_SEARCH_HEADER_TEMPLATE
-        assert context_template == DEFAULT_CONTEXT_TEMPLATE
+        assert (
+            header_template
+            == "knowledge_search tool found {num_chunks} chunks:\nBEGIN of knowledge_search tool results.\n"
+        )
+        assert (
+            context_template
+            == 'The above results were retrieved to help answer the user\'s query: "{query}". Use them as supporting information only in answering this query. {annotation_instruction}\n'
+        )
 
         # Verify templates can be formatted successfully
         formatted_header = header_template.format(num_chunks=3)

tests/unit/providers/vector_io/test_vector_io_openai_vector_stores.py

@@ -1091,13 +1091,11 @@ async def test_max_concurrent_files_per_batch(vector_io_adapter):
     # Give time for the semaphore logic to start processing files
     await asyncio.sleep(0.2)
 
-    # Verify that only MAX_CONCURRENT_FILES_PER_BATCH files are processing concurrently
+    # Verify that only max_concurrent_files_per_batch files are processing concurrently
     # The semaphore in _process_files_with_concurrency should limit this
-    from llama_stack.providers.utils.memory.openai_vector_store_mixin import MAX_CONCURRENT_FILES_PER_BATCH
+    max_concurrent_files = vector_io_adapter.vector_stores_config.file_batch_params.max_concurrent_files_per_batch
 
-    assert active_files == MAX_CONCURRENT_FILES_PER_BATCH, (
-        f"Expected {MAX_CONCURRENT_FILES_PER_BATCH} active files, got {active_files}"
-    )
+    assert active_files == max_concurrent_files, f"Expected {max_concurrent_files} active files, got {active_files}"
 
     # Verify batch is in progress
     assert batch.status == "in_progress"