Feat: Initialize context engine CLI (#13776)

### What problem does this PR solve?

- Add multiple output format to ragflow_cli
- Initialize contextengine to Go module
  - ls datasets/ls files
  - cat file
  - search -d dir -q query

issue: #13714

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

internal/cli/contextengine/README.md

@@ -0,0 +1,49 @@
+# ContextFS - Context Engine File System
+
+ContextFS is a context engine interface for RAGFlow, providing users with a Unix-like file system interface to manage datasets, tools, skills, and memories.
+
+## Directory Structure
+
+```
+user_id/
+├── datasets/
+│   └── my_dataset/
+│       └── ...
+├── tools/
+│   ├── registry.json
+│   └── tool_name/
+│       ├── DOC.md
+│       └── ...
+├── skills/
+│   ├── registry.json
+│   └── skill_name/
+│       ├── SKILL.md
+│       └── ...
+└── memories/
+    └── memory_id/
+        ├── sessions/
+        │   ├── messages/
+        │   ├── summaries/
+        │   │   └── session_id/
+        │   │       └── summary-{datetime}.md
+        │   └── tools/
+        │       └── session_id/
+        │           └── {tool_name}.md          # User level of memory on Tools usage
+        ├── users/
+        │   ├── profile.md
+        │   ├── preferences/
+        │   └── entities/
+        └── agents/
+            └── agent_space/
+                ├── tools/
+                │   └── {tool_name}.md          # Agent level of memory on Tools usage
+                └── skills/
+                    └── {skill_name}.md         # Agent level of memory on Skills usage
+```
+
+
+## Supported Commands
+
+- `ls [path]` - List directory contents
+- `cat <path>` - Display file contents(only for text files)
+- `search <query>` - Search content