Fix prompt template bugs: build template ignored and runtime override not wired (#173)

* Fix prompt template bugs in build and search

Bug 1: Build template ignored in new format
- Updated compute_embeddings_openai() to read build_prompt_template or prompt_template
- Updated compute_embeddings_ollama() with same fix
- Maintains backward compatibility with old single-template format

Bug 2: Runtime override not wired up
- Wired CLI search to pass provider_options to searcher.search()
- Enables runtime template override during search via --embedding-prompt-template

All 42 prompt template tests passing.

Fixes #155

* Fix: Prevent embedding server from applying templates during search

- Filter out all prompt templates (build_prompt_template, query_prompt_template, prompt_template) from provider_options when launching embedding server during search
- Templates are already applied in compute_query_embedding() before server call
- Prevents double-templating and ensures runtime override works correctly

This fixes the issue where --embedding-prompt-template during search was ignored because the server was applying build_prompt_template instead.

* Format code with ruff

packages/leann-core/src/leann/cli.py

@@ -1545,6 +1545,11 @@ Examples:
                         print("Invalid input. Aborting search.")
                         return
 
+        # Build provider_options for runtime override
+        provider_options = {}
+        if args.embedding_prompt_template:
+            provider_options["prompt_template"] = args.embedding_prompt_template
+
         searcher = LeannSearcher(index_path=index_path)
         results = searcher.search(
             query,
@@ -1554,6 +1559,7 @@ Examples:
             prune_ratio=args.prune_ratio,
             recompute_embeddings=args.recompute_embeddings,
             pruning_strategy=args.pruning_strategy,
+            provider_options=provider_options if provider_options else None,
         )
 
         print(f"Search results for '{query}' (top {len(results)}):")