feat(agent): two-stage memory system with Dream consolidation

Replace single-stage MemoryConsolidator with a two-stage architecture:

- Consolidator: lightweight token-budget triggered summarization,
  appends to HISTORY.md with cursor-based tracking
- Dream: cron-scheduled two-phase processor that analyzes HISTORY.md
  and updates SOUL.md, USER.md, MEMORY.md via AgentRunner with
  edit_file tools for surgical, fault-tolerant updates

New files: MemoryStore (pure file I/O), Dream class, DreamConfig,
/dream and /dream-log commands. 89 tests covering all components.

tests/cli/test_restart_command.py

@@ -127,7 +127,7 @@ class TestRestartCommand:
         loop.sessions.get_or_create.return_value = session
         loop._start_time = time.time() - 125
         loop._last_usage = {"prompt_tokens": 0, "completion_tokens": 0}
-        loop.memory_consolidator.estimate_session_prompt_tokens = MagicMock(
+        loop.consolidator.estimate_session_prompt_tokens = MagicMock(
             return_value=(20500, "tiktoken")
         )
 
@@ -166,7 +166,7 @@ class TestRestartCommand:
         session.get_history.return_value = [{"role": "user"}]
         loop.sessions.get_or_create.return_value = session
         loop._last_usage = {"prompt_tokens": 1200, "completion_tokens": 34}
-        loop.memory_consolidator.estimate_session_prompt_tokens = MagicMock(
+        loop.consolidator.estimate_session_prompt_tokens = MagicMock(
             return_value=(0, "none")
         )