v0.74.1

Documentation accuracy fixes:

• Fix incorrect MCP tool name (keep_tag_update → keep_tag) in agent guide
• Fix nonexistent MCP parameters in agent guide examples
• Add deep, show_tags, token_budget to MCP keep_find docs
• Add --deep, --tags, --tokens to CLI find docs
• Update version selector help text for negative selectors
• Remove reference to nonexistent --no-similar flag
• Fix broken REST-API.md link
• Add negative version selectors to reference card