fix: add offline-llm extra and always sync venv on shell entry

ollama python package is in the offline-llm extra, not api.
Always run uv sync (not just on first entry) so extra changes take effect.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

flake.nix

@@ -55,10 +55,8 @@
             export LD_LIBRARY_PATH="${pkgs.lib.makeLibraryPath [ pkgs.stdenv.cc.cc pkgs.zlib ]}:$LD_LIBRARY_PATH"
             cd "$RAGS_ROOT/lightrag"
 
-            if [ ! -d .venv ]; then
-              echo "Setting up lightrag venv (first time, ~2min)..."
-              uv sync --extra api --quiet
-            fi
+            echo "Syncing lightrag venv..."
+            uv sync --extra api --extra offline-llm --quiet
             source .venv/bin/activate
 
             if [ -f "$RAGS_ROOT/.env.lightrag" ]; then
@@ -85,10 +83,8 @@
             export LD_LIBRARY_PATH="${pkgs.lib.makeLibraryPath [ pkgs.stdenv.cc.cc pkgs.zlib ]}:$LD_LIBRARY_PATH"
             cd "$RAGS_ROOT/graphiti"
 
-            if [ ! -d .venv ]; then
-              echo "Setting up graphiti venv (first time, ~1min)..."
-              uv sync --quiet
-            fi
+            echo "Syncing graphiti venv..."
+            uv sync --quiet
             source .venv/bin/activate
 
             if [ -f "$RAGS_ROOT/.env.graphiti" ]; then