fix: clean and simple hang prevention solution

This commit provides a minimal, focused fix for CI hanging issues by addressing the root causes:

**Key Changes:**

1. **ZMQ Resource Management:**
   - Remove `context.term()` calls that were causing hangs
   - Add `socket.setsockopt(zmq.LINGER, 0)` to prevent blocking on close
   - Keep socket operations simple with default timeouts (no artificial limits)

2. **Process Cleanup:**
   - Add timeout (1s) to final `process.wait()` in embedding server manager
   - Prevent infinite waiting that was causing CI hangs

3. **Resource Cleanup Methods:**
   - Add simple `cleanup()` methods to searchers and API classes
   - Focus on C++ object destruction for DiskANN backend
   - Avoid complex cleanup logic that could introduce new issues

4. **Basic Test Safety:**
   - Simple pytest-timeout configuration (300s)
   - Basic test session cleanup using psutil
   - Minimal conftest.py without complex logic

**Philosophy:**
This solution avoids the complex multi-layered fixes from the previous PR chain.
Instead, it targets the specific root causes:
- ZMQ context termination blocking
- Process wait() without timeout
- C++ resource leaks in backends

🤖 Generated with [Claude Code](https://claude.ai/code)

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

pyproject.toml

@@ -60,7 +60,7 @@ dev = [
 
 test = [
     "pytest>=7.0",
-    "pytest-timeout>=2.0",
+    "pytest-timeout>=2.0",  # Simple timeout protection for CI
     "llama-index-core>=0.12.0",
     "llama-index-readers-file>=0.4.0",
     "python-dotenv>=1.0.0",
@@ -152,7 +152,7 @@ markers = [
     "slow: marks tests as slow (deselect with '-m \"not slow\"')",
     "openai: marks tests that require OpenAI API key",
 ]
-timeout = 600
+timeout = 300  # Simple timeout for CI safety (5 minutes)
 addopts = [
     "-v",
     "--tb=short",