feat: Always enable embeddings, remove enableEmbeddings config option

Testing showed semantic search produces significantly better results for
natural language queries that Claude writes. FTS alone often ranks
properties above their parent classes and misses conceptual matches.
Embeddings are now always on — the vector manager is created eagerly,
with model download and embedding generation still happening lazily.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -645,8 +645,7 @@ The `.codegraph/config.json` file controls indexing behavior:
   "frameworks": [],
   "maxFileSize": 1048576,
   "extractDocstrings": true,
-  "trackCallSites": true,
-  "enableEmbeddings": false
+  "trackCallSites": true
 }
 ```
 
@@ -660,7 +659,6 @@ The `.codegraph/config.json` file controls indexing behavior:
 | `maxFileSize` | Skip files larger than this (bytes) | `1048576` (1MB) |
 | `extractDocstrings` | Whether to extract docstrings from code | `true` |
 | `trackCallSites` | Whether to track call site locations | `true` |
-| `enableEmbeddings` | Enable semantic search embeddings | `false` |
 
 ## 🌐 Supported Languages