fix: remove FAISS requirement from ai-enhanced feature

Changes:
- ai-enhanced no longer requires faiss (only needs embeddings)
- Added ai-enhanced-faiss for backward compatibility
- Fixed cloud_search_impl feature gate (cloud not embeddings)
- Unconditionally import std::time::Instant (used in non-FAISS code)

This allows building agentic tools without FAISS system library.
Agentic tools only use SurrealDB, not FAISS vector search.

Author: jruokola

crates/codegraph-mcp/Cargo.toml

@@ -93,6 +93,7 @@ embeddings-jina = ["embeddings", "codegraph-vector/jina"]
 cloud = ["embeddings-jina", "codegraph-graph/surrealdb"]
 server-http = ["dep:axum", "dep:hyper", "dep:tower", "dep:http-body-util"]
 qwen-integration = []
-ai-enhanced = ["dep:codegraph-ai", "faiss", "embeddings"]
+ai-enhanced = ["dep:codegraph-ai", "embeddings"]
+ai-enhanced-faiss = ["ai-enhanced", "faiss"]
 autoagents-experimental = ["dep:autoagents", "dep:autoagents-derive"]
 legacy-mcp-server = []

crates/codegraph-mcp/src/server.rs

@@ -8,7 +8,6 @@ use serde_json::Value;
 #[cfg(any(feature = "faiss", feature = "legacy-mcp-server"))]
 use std::path::PathBuf;
 use std::sync::Arc;
-#[cfg(any(feature = "faiss", feature = "cloud", feature = "legacy-mcp-server"))]
 use std::time::Instant;
 
 // Performance optimization: Cache FAISS indexes and embedding generator
@@ -1197,14 +1196,14 @@ pub async fn bin_search_with_scores_shared(
 
     match mode {
         SearchMode::Cloud => {
-            #[cfg(feature = "embeddings")]
+            #[cfg(feature = "cloud")]
             {
                 cloud_search_impl(_query, _paths, _langs, _limit, _graph).await
             }
-            #[cfg(not(feature = "embeddings"))]
+            #[cfg(not(feature = "cloud"))]
             {
                 Err(anyhow::anyhow!(
-                    "Cloud mode requires embeddings feature. Rebuild with --features embeddings"
+                    "Cloud mode requires cloud feature. Rebuild with --features cloud"
                 ))
             }
         }