feat: MemPalace integration — skill port, retrieval enforcer, wake-up protocol (#367)

MP-1 (#368): Port PalaceRoom + Mempalace classes with 22 unit tests
MP-2 (#369): L0-L5 retrieval order enforcer with recall-query detection
MP-5 (#372): Wake-up protocol (300-900 token context), session scratchpad

Modules:
- mempalace.py: PalaceRoom + Mempalace dataclasses, factory constructors
- retrieval_enforcer.py: Layered memory retrieval (identity → palace → scratch → gitea → skills)
- wakeup.py: Session wake-up with caching (5min TTL)
- scratchpad.py: JSON-based session notes with palace promotion

All 65 tests pass. Pure stdlib + graceful degradation for ONNX issues (#373).

hermes-sovereign/mempalace/tests/test_scratchpad.py

@@ -0,0 +1,108 @@
+"""Tests for scratchpad.py.
+
+Refs: Epic #367, Sub-issue #372
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import sys
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", ".."))
+
+from mempalace.scratchpad import (
+    write_scratch,
+    read_scratch,
+    delete_scratch,
+    list_sessions,
+    clear_session,
+    _scratch_path,
+)
+
+
+@pytest.fixture
+def scratch_dir(tmp_path):
+    """Provide a temporary scratchpad directory."""
+    with patch("mempalace.scratchpad.SCRATCHPAD_DIR", tmp_path):
+        yield tmp_path
+
+
+class TestScratchPath:
+    def test_sanitizes_session_id(self):
+        path = _scratch_path("safe-id_123")
+        assert "safe-id_123.json" in str(path)
+
+    def test_strips_dangerous_chars(self):
+        path = _scratch_path("../../etc/passwd")
+        assert ".." not in path.name
+        assert "/" not in path.name
+        # Dots are stripped, so only alphanumeric chars remain
+        assert path.name == "etcpasswd.json"
+
+
+class TestWriteAndRead:
+    def test_write_then_read(self, scratch_dir):
+        write_scratch("sess1", "note", "hello world")
+        result = read_scratch("sess1", "note")
+        assert "note" in result
+        assert result["note"]["value"] == "hello world"
+
+    def test_read_all_keys(self, scratch_dir):
+        write_scratch("sess1", "a", 1)
+        write_scratch("sess1", "b", 2)
+        result = read_scratch("sess1")
+        assert "a" in result
+        assert "b" in result
+
+    def test_read_missing_key(self, scratch_dir):
+        write_scratch("sess1", "exists", "yes")
+        result = read_scratch("sess1", "missing")
+        assert result == {}
+
+    def test_read_missing_session(self, scratch_dir):
+        result = read_scratch("nonexistent")
+        assert result == {}
+
+    def test_overwrite_key(self, scratch_dir):
+        write_scratch("sess1", "key", "v1")
+        write_scratch("sess1", "key", "v2")
+        result = read_scratch("sess1", "key")
+        assert result["key"]["value"] == "v2"
+
+
+class TestDelete:
+    def test_delete_existing_key(self, scratch_dir):
+        write_scratch("sess1", "key", "val")
+        assert delete_scratch("sess1", "key") is True
+        assert read_scratch("sess1", "key") == {}
+
+    def test_delete_missing_key(self, scratch_dir):
+        write_scratch("sess1", "other", "val")
+        assert delete_scratch("sess1", "missing") is False
+
+
+class TestListSessions:
+    def test_lists_sessions(self, scratch_dir):
+        write_scratch("alpha", "k", "v")
+        write_scratch("beta", "k", "v")
+        sessions = list_sessions()
+        assert "alpha" in sessions
+        assert "beta" in sessions
+
+    def test_empty_directory(self, scratch_dir):
+        assert list_sessions() == []
+
+
+class TestClearSession:
+    def test_clears_existing(self, scratch_dir):
+        write_scratch("sess1", "k", "v")
+        assert clear_session("sess1") is True
+        assert read_scratch("sess1") == {}
+
+    def test_clear_nonexistent(self, scratch_dir):
+        assert clear_session("ghost") is False