Add an examples overview README

[CaralHsi]

The examples/ directory currently does not have a top-level README. This makes it harder for new users to discover which examples are available and where to start.

Target file

• examples/README.md

Suggested content

The README should briefly describe the purpose of each examples subdirectory, including:

• api
• basic_modules
• core_memories
• dream
• extras
• mem_agent
• mem_chat
• mem_cube
• mem_feedback
• mem_mcp
• mem_reader
• mem_scheduler

Requirements

• Keep descriptions concise.
• Add basic guidance on how to run examples, if applicable.
• Link to more detailed docs under docs/ where available.
• Do not modify example code.

Acceptance Criteria

• examples/README.md exists.
• Main example categories are listed and described.
• Markdown renders correctly.