bench: add benchmark runners, results docs, and test suite

Benchmarks: LongMemEval, LoCoMo, ConvoMem, MemBench runners with
methodology docs and hybrid retrieval analysis.

Tests: config, miner, convo_miner, normalize — 9 tests, all passing.

tests/test_convo_miner.py

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+import os
+import tempfile
+import shutil
+import chromadb
+from mempalace.convo_miner import mine_convos
+
+
+def test_convo_mining():
+    tmpdir = tempfile.mkdtemp()
+    with open(os.path.join(tmpdir, "chat.txt"), "w") as f:
+        f.write(
+            "> What is memory?\nMemory is persistence.\n\n> Why does it matter?\nIt enables continuity.\n\n> How do we build it?\nWith structured storage.\n"
+        )
+
+    palace_path = os.path.join(tmpdir, "palace")
+    mine_convos(tmpdir, palace_path, wing="test_convos")
+
+    client = chromadb.PersistentClient(path=palace_path)
+    col = client.get_collection("mempalace_drawers")
+    assert col.count() >= 2
+
+    # Verify search works
+    results = col.query(query_texts=["memory persistence"], n_results=1)
+    assert len(results["documents"][0]) > 0
+
+    shutil.rmtree(tmpdir)