Add AI Council architecture: Tier 2/3/Graph implementation + Integration Plan

Architecture (Agent 1):
- hermes_memory/tier2/{schema,facts,entities,relations,timeline}.py
- hermes_memory/tier3/{backend,chroma_backend,embedder}.py
- hermes_memory/graph/nx_store.py
- hermes_memory/api/memory_api.py (unified API)
- hermes_memory/cron/{consolidate,embed_queue,graph_refresh,prune}.py
- hermes_memory/config.py + pyproject.toml

Integration Plan (Agent 3):
- INTEGRATION_PLAN.md: Memory Provider Plugin strategy
- Hermes Core needs minimal changes
- sync_turn() + prefetch() hooks
- Skills integration via nextlevel_search/remember

Auto-Extraction (Agent 2):
- ARCHITECTURE.md: Full extraction pipeline docs
- Chunking, Pre-Filter, LLM Prompts, Classification
- Entity-Linking, Temporal Reasoning, Deduplication

All files: Python syntax checked, ECC standards applied.

hermes_memory/tier3/chroma_backend.py

@@ -0,0 +1,69 @@
+"""Chroma-Implementierung des VectorBackend."""
+
+import logging
+from pathlib import Path
+from typing import Dict, List, Optional
+
+from hermes_memory.tier3.backend import SearchResult, VectorBackend
+
+logger = logging.getLogger(__name__)
+
+
+class ChromaBackend(VectorBackend):
+    def __init__(self, persist_path: Path, collection_name: str = "memory_chunks"):
+        self.persist_path = persist_path
+        self.collection_name = collection_name
+        self._client = None
+        self._collection = None
+        self._init()
+
+    def _init(self) -> None:
+        try:
+            import chromadb
+            self._client = chromadb.PersistentClient(path=str(self.persist_path))
+            self._collection = self._client.get_or_create_collection(
+                name=self.collection_name,
+                metadata={"hnsw:space": "cosine"},
+            )
+        except ImportError:
+            logger.error("chromadb nicht installiert. Installiere: pip install chromadb")
+            raise
+
+    def index(self, chunks: List[str], payloads: List[Dict]) -> List[str]:
+        if not chunks:
+            return []
+        chunk_ids = [p.get("chunk_id", f"chunk_{i}") for i, p in enumerate(payloads)]
+        self._collection.add(
+            ids=chunk_ids,
+            documents=chunks,
+            metadatas=payloads,
+        )
+        return chunk_ids
+
+    def search(self, query_embedding: List[float], limit: int = 10, filters: Dict = None) -> List[SearchResult]:
+        results = self._collection.query(
+            query_embeddings=[query_embedding],
+            n_results=limit,
+            where=filters,
+        )
+        out: List[SearchResult] = []
+        if not results["ids"]:
+            return out
+        for i, cid in enumerate(results["ids"][0]):
+            out.append(
+                SearchResult(
+                    chunk_id=cid,
+                    score=results["distances"][0][i],
+                    text=results["documents"][0][i] or "",
+                    metadata=results["metadatas"][0][i] or {},
+                )
+            )
+        return out
+
+    def delete(self, chunk_ids: List[str]) -> bool:
+        self._collection.delete(ids=chunk_ids)
+        return True
+
+    def health(self) -> Dict:
+        count = self._collection.count()
+        return {"backend": "chroma", "collection": self.collection_name, "count": count}