docs(refactor-module-logic): Clarify data model and module responsibilities

docs(refactor-module-logic): Clarify data model and module responsibilities This commit incorporates clarifications into the 'refactor-module-logic' specification (003). Two key ambiguities were resolved: 1. **New field for cleaned content**: The and data models will now include a field to store content with Logseq-specific properties removed. This field will retain accurate Markdown, links, and formatting. 2. **Module responsibility**: The parsing module is assigned the responsibility of populating this field during initial parsing. This ensures the module receives pre-processed data ready for conversion to Markdown. These clarifications enhance the data model's definition and streamline module responsibilities, supporting the core refactoring goals.