Title: [CRITICAL] Data Persistence Failure & Faulty Error Handling: mempalace_add_drawer reports success despite result: null in logs*

Description

A critical bug has been identified in the MemPalace architecture involving two interconnected issues:

1. Data Persistence Failure: The tool mempalace_add_drawer fails to physically write data to the persistent storage, even though the command is logged.
2. Faulty Error Handling Logic (Agent-side): The Agent interprets a null result in the execution logs as a successful operation because no explicit error message is returned, leading to a false sense of data integrity.

Steps to Reproduce

1. Initialize a session and attempt to create a new wing/drawer using mempalace_add_drawer (e.g., creating testwing2 with content: "Ich habe in meinem Leben schon diese Obstsorten gegessen").
2. Observe the Agent's response: The tool execution log or the agent's interpretation indicates a successful operation (the agent receives a response from the tool).
3. Verify via inspection: Run mempalace_list_wings or mempalace_list_drawers in a new session/chat.
4. Result: The newly created wing/drawer is missing from the list.

Expected Behavior

• Persistence: The tool mempalance_add_drawer must ensure that once an operation is initiated, the data is physically written to the persistent storage and is retrievable in subsequent sessions.
• Error Handling: The system should not return null for a failed write operation. Furthermore, the Agent's logic must be updated to treat a result: null in the execution log as a failure/error rather than a success.

Actual Behavior

The system suffers from a "Silent Write Failure".

• Investigation of wal/write_log.jsonl reveals that while the command is logged, the result field for the operation often returns null.
• Agent-side Error: The Agent interprets the lack of an explicit error string as a success, masking the fact that the underlying database transaction failed.
• Data disappears immediately after the session ends or even before the next command in the same session can verify it.

Evidence (Logs)

Tool Output observed during execution (Agent's view):

{
  "status": "success",
  "drawer_id": "drawer_test_wing_experiment_kirschen_7a2b8c9d1e3f4g5h6i7j",
  "wing": "test_wing",
  "room": "experiment",
  "content_preview": "Ich habe in meinem Leben schon diese Obstsorten gegessen",
  "timestamp": "2026-04-13T18:05:12Z"
}

Discrepancy in wal/write_log.jsonl (System Truth):
The log entry for the same operation shows:
"result": null

Environment/Context

• OS: Mac OS 26.3.1 (a)
• HArdware: MacBook M4 Pro 48GB RAM
• MODEL: Gemma 4 27b
• Component: MemPalace Toolset / Backend Persistence Layer / Agent Error-Handling Logic
• Severity: Critical (Data Loss & False Positive Reporting)