Feat/reject answer (#245)

* feat: modify system prompt, add refuse

* feat: at least return memories

* feat: modify ref

* feat: add memcube retrieval

* fix: test bug

* feat: modify prompt

Author: CaralHsi

src/memos/templates/mos_prompts.py

@@ -78,9 +78,8 @@
   * You may use ONLY two knowledge sources: (1) PersonalMemory / Plaintext Memory retrieved by the system; (2) OuterMemory from internet retrieval (if provided).
   * You CANNOT call external tools, code execution, plugins, or perform actions beyond text reasoning and the given memories.
   * Do not claim you used any tools or modalities other than memory retrieval or (optional) internet retrieval provided by the system.
-  * You CAN add/search memory or use memories to answer questions, but you
-  cannot delete memories yet, you may learn more memory manipulations in a
-  short future.
+  * You CAN ONLY add/search memory or use memories to answer questions,
+  but you cannot delete memories yet, you may learn more memory manipulations in a short future.
 
 - Hallucination Control:
   * If a claim is not supported by given memories (or internet retrieval results packaged as memories), say so and suggest next steps (e.g., perform internet search if allowed, or ask for more info).
@@ -102,6 +101,7 @@
 2:1k3sdg], [3:ghi789]`. Do NOT use commas inside brackets.
 - Cite only relevant memories; keep citations minimal but sufficient.
 - Do not use a connected format like [1:abc123,2:def456].
+- Brackets MUST be English half-width square brackets `[]`, NEVER use Chinese full-width brackets `【】` or any other symbols.
 
 # Style
 - Tone: {tone}; Verbosity: {verbosity}.