pi-memory v1.3.1

Changes

• Fix: frontmatter description now stays in sync with MEMORY.md hook on add/remove
• Refactor: extract agent uses memory tools (memory_add + memory_search) instead of raw file I/O
• Refactor: extension memory tool removed 'read' action, use built-in read/ls instead
• Refactor: side-query runs with zero built-in tools
• Chore: rename MEMORY_AGENT_TOOLS → FILE_IO_TOOLS
• Chore: remove dead doRead code
• Docs: update READMEs to reflect new tool signatures