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/test_knowledge_graph.py

@@ -0,0 +1,124 @@
+"""
+test_knowledge_graph.py — Tests for the temporal knowledge graph.
+
+Covers: entity CRUD, triple CRUD, temporal queries, invalidation,
+timeline, stats, and edge cases (duplicate triples, ID collisions).
+"""
+
+from mempalace.knowledge_graph import KnowledgeGraph
+
+
+class TestEntityOperations:
+    def test_add_entity(self, kg):
+        eid = kg.add_entity("Alice", entity_type="person")
+        assert eid == "alice"
+
+    def test_add_entity_normalizes_id(self, kg):
+        eid = kg.add_entity("Dr. Chen", entity_type="person")
+        assert eid == "dr._chen"
+
+    def test_add_entity_upsert(self, kg):
+        kg.add_entity("Alice", entity_type="person")
+        kg.add_entity("Alice", entity_type="engineer")
+        # Should not raise — INSERT OR REPLACE
+        stats = kg.stats()
+        assert stats["entities"] == 1
+
+
+class TestTripleOperations:
+    def test_add_triple_creates_entities(self, kg):
+        tid = kg.add_triple("Alice", "knows", "Bob")
+        assert tid.startswith("t_alice_knows_bob_")
+        stats = kg.stats()
+        assert stats["entities"] == 2  # auto-created
+
+    def test_add_triple_with_dates(self, kg):
+        tid = kg.add_triple("Max", "does", "swimming", valid_from="2025-01-01")
+        assert tid.startswith("t_max_does_swimming_")
+
+    def test_duplicate_triple_returns_existing_id(self, kg):
+        tid1 = kg.add_triple("Alice", "knows", "Bob")
+        tid2 = kg.add_triple("Alice", "knows", "Bob")
+        assert tid1 == tid2
+
+    def test_invalidated_triple_allows_re_add(self, kg):
+        tid1 = kg.add_triple("Alice", "works_at", "Acme")
+        kg.invalidate("Alice", "works_at", "Acme", ended="2025-01-01")
+        tid2 = kg.add_triple("Alice", "works_at", "Acme")
+        assert tid1 != tid2  # new triple since old one was closed
+
+
+class TestQueries:
+    def test_query_outgoing(self, seeded_kg):
+        results = seeded_kg.query_entity("Alice", direction="outgoing")
+        predicates = {r["predicate"] for r in results}
+        assert "parent_of" in predicates
+        assert "works_at" in predicates
+
+    def test_query_incoming(self, seeded_kg):
+        results = seeded_kg.query_entity("Max", direction="incoming")
+        assert any(r["subject"] == "Alice" and r["predicate"] == "parent_of" for r in results)
+
+    def test_query_both_directions(self, seeded_kg):
+        results = seeded_kg.query_entity("Max", direction="both")
+        directions = {r["direction"] for r in results}
+        assert "outgoing" in directions
+        assert "incoming" in directions
+
+    def test_query_as_of_filters_expired(self, seeded_kg):
+        results = seeded_kg.query_entity("Alice", as_of="2023-06-01", direction="outgoing")
+        employers = [r["object"] for r in results if r["predicate"] == "works_at"]
+        assert "Acme Corp" in employers
+        assert "NewCo" not in employers
+
+    def test_query_as_of_shows_current(self, seeded_kg):
+        results = seeded_kg.query_entity("Alice", as_of="2025-06-01", direction="outgoing")
+        employers = [r["object"] for r in results if r["predicate"] == "works_at"]
+        assert "NewCo" in employers
+        assert "Acme Corp" not in employers
+
+    def test_query_relationship(self, seeded_kg):
+        results = seeded_kg.query_relationship("does")
+        assert len(results) == 2  # swimming + chess
+
+
+class TestInvalidation:
+    def test_invalidate_sets_valid_to(self, seeded_kg):
+        seeded_kg.invalidate("Max", "does", "chess", ended="2026-01-01")
+        results = seeded_kg.query_entity("Max", direction="outgoing")
+        chess = [r for r in results if r["object"] == "chess"]
+        assert len(chess) == 1
+        assert chess[0]["valid_to"] == "2026-01-01"
+        assert chess[0]["current"] is False
+
+
+class TestTimeline:
+    def test_timeline_all(self, seeded_kg):
+        tl = seeded_kg.timeline()
+        assert len(tl) >= 4
+
+    def test_timeline_entity(self, seeded_kg):
+        tl = seeded_kg.timeline("Max")
+        subjects_and_objects = {t["subject"] for t in tl} | {t["object"] for t in tl}
+        assert "Max" in subjects_and_objects
+
+    def test_timeline_global_has_limit(self, kg):
+        # Add > 100 triples
+        for i in range(105):
+            kg.add_triple(f"entity_{i}", "relates_to", f"entity_{i + 1}")
+        tl = kg.timeline()
+        assert len(tl) == 100  # LIMIT 100
+
+
+class TestStats:
+    def test_stats_empty(self, kg):
+        stats = kg.stats()
+        assert stats["entities"] == 0
+        assert stats["triples"] == 0
+
+    def test_stats_seeded(self, seeded_kg):
+        stats = seeded_kg.stats()
+        assert stats["entities"] >= 4
+        assert stats["triples"] == 5
+        assert stats["current_facts"] == 4  # 1 expired (Acme Corp)
+        assert stats["expired_facts"] == 1