test: expand coverage from 20 to 92 tests, migrate to uv

- Migrate from setuptools to hatchling build backend
- Add dependency-groups (PEP 735) for dev tooling (pytest, ruff)
- Remove redundant requirements.txt in favor of uv.lock
- Fix __version__ mismatch (2.0.0 -> 3.0.0 to match pyproject.toml)

New test files:
- conftest.py: shared fixtures (isolated palace, KG, ChromaDB collection)
- test_knowledge_graph.py: 17 tests (entity CRUD, temporal queries, timeline)
- test_mcp_server.py: 25 tests (protocol dispatch, read/write/KG/diary tools)
- test_searcher.py: 7 tests (search_memories API, filters, error handling)
- test_dialect.py: 13 tests (AAAK compression, entity/emotion detection, zettel encoding)

All 92 tests pass on Python 3.13 with chromadb 0.6.3.

tests/conftest.py

@@ -0,0 +1,106 @@
+"""
+conftest.py — Shared fixtures for MemPalace tests.
+
+Provides isolated palace and knowledge graph instances so tests never
+touch the user's real data or leak temp files on failure.
+"""
+
+import os
+import shutil
+import tempfile
+
+import chromadb
+import pytest
+
+from mempalace.config import MempalaceConfig
+from mempalace.knowledge_graph import KnowledgeGraph
+
+
+@pytest.fixture
+def tmp_dir():
+    """Create and auto-cleanup a temporary directory."""
+    d = tempfile.mkdtemp(prefix="mempalace_test_")
+    yield d
+    shutil.rmtree(d, ignore_errors=True)
+
+
+@pytest.fixture
+def palace_path(tmp_dir):
+    """Path to an empty palace directory inside tmp_dir."""
+    p = os.path.join(tmp_dir, "palace")
+    os.makedirs(p)
+    return p
+
+
+@pytest.fixture
+def config(tmp_dir, palace_path):
+    """A MempalaceConfig pointing at the temp palace."""
+    cfg_dir = os.path.join(tmp_dir, "config")
+    os.makedirs(cfg_dir)
+    import json
+
+    with open(os.path.join(cfg_dir, "config.json"), "w") as f:
+        json.dump({"palace_path": palace_path}, f)
+    return MempalaceConfig(config_dir=cfg_dir)
+
+
+@pytest.fixture
+def collection(palace_path):
+    """A ChromaDB collection pre-seeded in the temp palace."""
+    client = chromadb.PersistentClient(path=palace_path)
+    col = client.get_or_create_collection("mempalace_drawers")
+    return col
+
+
+@pytest.fixture
+def seeded_collection(collection):
+    """Collection with a handful of representative drawers."""
+    collection.add(
+        ids=[
+            "drawer_proj_backend_aaa",
+            "drawer_proj_backend_bbb",
+            "drawer_proj_frontend_ccc",
+            "drawer_notes_planning_ddd",
+        ],
+        documents=[
+            "The authentication module uses JWT tokens for session management. "
+            "Tokens expire after 24 hours. Refresh tokens are stored in HttpOnly cookies.",
+            "Database migrations are handled by Alembic. We use PostgreSQL 15 "
+            "with connection pooling via pgbouncer.",
+            "The React frontend uses TanStack Query for server state management. "
+            "All API calls go through a centralized fetch wrapper.",
+            "Sprint planning: migrate auth to passkeys by Q3. "
+            "Evaluate ChromaDB alternatives for vector search.",
+        ],
+        metadatas=[
+            {"wing": "project", "room": "backend", "source_file": "auth.py", "chunk_index": 0, "added_by": "miner", "filed_at": "2026-01-01T00:00:00"},
+            {"wing": "project", "room": "backend", "source_file": "db.py", "chunk_index": 0, "added_by": "miner", "filed_at": "2026-01-02T00:00:00"},
+            {"wing": "project", "room": "frontend", "source_file": "App.tsx", "chunk_index": 0, "added_by": "miner", "filed_at": "2026-01-03T00:00:00"},
+            {"wing": "notes", "room": "planning", "source_file": "sprint.md", "chunk_index": 0, "added_by": "miner", "filed_at": "2026-01-04T00:00:00"},
+        ],
+    )
+    return collection
+
+
+@pytest.fixture
+def kg(tmp_dir):
+    """An isolated KnowledgeGraph using a temp SQLite file."""
+    db_path = os.path.join(tmp_dir, "test_kg.sqlite3")
+    return KnowledgeGraph(db_path=db_path)
+
+
+@pytest.fixture
+def seeded_kg(kg):
+    """KnowledgeGraph pre-loaded with sample triples."""
+    kg.add_entity("Alice", entity_type="person")
+    kg.add_entity("Max", entity_type="person")
+    kg.add_entity("swimming", entity_type="activity")
+    kg.add_entity("chess", entity_type="activity")
+
+    kg.add_triple("Alice", "parent_of", "Max", valid_from="2015-04-01")
+    kg.add_triple("Max", "does", "swimming", valid_from="2025-01-01")
+    kg.add_triple("Max", "does", "chess", valid_from="2024-06-01")
+    kg.add_triple("Alice", "works_at", "Acme Corp", valid_from="2020-01-01", valid_to="2024-12-31")
+    kg.add_triple("Alice", "works_at", "NewCo", valid_from="2025-01-01")
+
+    return kg