docs: Update documentation and rules for tagged task lists system

- Updated task-structure.md with comprehensive tagged format explanation
- Updated all .cursor/rules/*.mdc files to reflect tagged system
- Completed subtask 103.16: Update Documentation for Tagged Task Lists System

.changeset/six-cups-see.md

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+---
+"task-master-ai": minor
+---
+
+Introduces tagged task lists for multi-context task management
+
+This release adds support for organizing tasks into separate lists (tags) to enable working across multiple contexts such as different branches, environments, or project phases without conflicts.
+
+**New Features:**
+
+- **Tagged Task Lists**: Organize tasks into separate contexts with tags like "master", "feature-branch", or "v2.0"
+- **Seamless Migration**: Existing projects automatically migrate to use a "master" tag with zero disruption
+- **Backward Compatibility**: All existing commands continue to work exactly as before
+- **Tag Management**: Commands to create, switch between, and manage different task contexts
+- **Git Integration**: Automatically create tags based on git branch names
+- **Context Isolation**: Tasks in different tags are completely separate and isolated
+
+**Migration:**
+
+- Existing `tasks.json` files are automatically migrated to the new tagged format
+- Your tasks will appear under the "master" tag by default
+- No action required - migration happens transparently on first use
+- All existing workflows continue to work unchanged
+
+**Coming in Part 2:**
+
+- CLI commands for tag management (`add-tag`, `use-tag`, `list-tags`)
+- MCP tool support for tag operations
+- Enhanced git branch integration
+- Tag switching and context management