docs: add ReMe2 architecture design documentation
- Add comprehensive design document (reme2.md) detailing the
three-layer architecture (L1/L2/L3) for the vault system
- Document new protocols for folder notes and memory management
- Specify interface contracts for memory_* and vault_* tools
- Outline implementation phases from current state to target
refactor: fix typo in personal retriever class
- Correct spelling error: 'retri eved_nodes' -> 'retrieved_nodes'
in PersonalRetriever.result assignment
chore: update gitignore with vault-related patterns
- Add '/vault' to ignore vault directory
- Add '/reme-plugin' to ignore plugin files
- Add '/reme2/vault' to ignore new vault implementation
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- Introduce BaseFileParser abstract class with component registration
- Add MdFileParser implementation for markdown files with YAML frontmatter
- Create TextFileParser implementation with built-in chunking support
- Implement file suffix enumeration for parser type safety
- Add chunking logic with configurable token size and overlap
- Support text file parsing with error handling for encoding issues
- Include line number tracking and content hashing for file chunks
