feat(memory): add native MemPalace memory provider plugin

plugins/memory/mempalace/README.md

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+# MemPalace Memory Provider
+
+Native [MemPalace](https://github.com/MemPalace/mempalace) integration for Hermes Agent — replaces the MCP bridge with direct Python API calls for lower latency and richer integration.
+
+## Features
+
+- **Semantic search** over the palace graph (L0 closets + L1 memories)
+- **Knowledge Graph** queries and updates
+- **Automatic diary journaling** at session end
+- **Turn archiving** — conversations automatically mined into the palace
+- **Background prefetch** — pre-warms recall for the next turn
+- **Tool exposure** — 5 tools available to the model
+
+## Tools
+
+| Tool | Description |
+|------|-------------|
+| `mempalace_search` | Semantic search across all palace drawers |
+| `mempalace_kg_query` | Query structured facts in the Knowledge Graph |
+| `mempalace_kg_add` | Add or invalidate KG facts |
+| `mempalace_diary_read` | Read recent diary entries |
+| `mempalace_diary_write` | Write diary entries (AAAK format) |
+
+## Setup
+
+1. **Install MemPalace** (if not already):
+   ```bash
+   pip install mempalace
+   ```
+
+2. **Initialize MemPalace** (first time only):
+   ```bash
+   mempalace init --palace /root/.mempalace/palace
+   ```
+
+3. **Configure Hermes**:
+   ```bash
+   # Option A: env var
+   export MEMPALACE_PATH=/root/.mempalace/palace
+
+   # Option B: set in Hermes
+   hermes memory setup
+   # Select "mempalace" when prompted
+   ```
+
+4. **Activate**:
+   ```bash
+   hermes config set memory.provider mempalace
+   ```
+   Then start a new session (`/reset` or restart the gateway).
+
+## Configuration
+
+| Config key | Default | Description |
+|-----------|---------|-------------|
+| `palace_path` | `/root/.mempalace/palace` | Path to the palace directory |
+| `agent_name` | `jarvis` | Agent identifier for diary |
+
+Set via `hermes memory setup` or directly in `config.yaml`:
+```yaml
+memory:
+  provider: mempalace
+  mempalace:
+    palace_path: /root/.mempalace/palace
+    agent_name: jarvis
+```
+
+## How It Works
+
+- `prefetch()` is called before each LLM API call, injecting semantic recall context
+- `queue_prefetch()` pre-warms the next turn's recall in the background
+- `sync_turn()` archives completed turns to the palace in real time
+- `on_session_end()` writes a diary entry summarizing the session
+- `on_memory_write()` mirrors built-in memory writes to MemPalace
+
+## Architecture
+
+```
+plugins/memory/mempalace/
+├── __init__.py      # MemPalaceMemoryProvider + register()
+├── plugin.yaml      # Metadata
+└── README.md        # This file
+```
+
+## Requirements
+
+- Python 3.10+
+- mempalace >= 3.0
+- chromadb (installed by mempalace)
+
+## Upstream
+
+This plugin is part of the MemPalace native integration for Hermes Agent.
+Contributions welcome: https://github.com/NousResearch/hermes-agent