feat: task graph loading

[wan9chi]

feat: Add vite_task_graph crate for task dependency management

This PR introduces a new vite_task_graph crate that provides a robust implementation for building and managing task dependency graphs in monorepo workspaces. The crate handles package discovery, task resolution, and dependency tracking between tasks.

Key changes:

• Created new vite_task_graph crate with clean API for task graph management
• Implemented TaskGraph structure to represent task dependencies with proper edge types
• Added support for explicit and topological dependency types
• Migrated test fixtures from vite_task to vite_task_graph for better organization
• Added snapshot testing for task graph validation
• Renamed get_package_graph to discover_package_graph and added load_package_graph in workspace module

[wan9chi]

• feat: task graph loading #48 👈 (View in Graphite)
• main

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