feat(tree): sort tasks by Taskfile definition order

[kyrokode]

Summary

• When taskfile.tree.sort is set to "default", tasks and namespaces in the sidebar are now sorted by their location.line property, preserving the original definition order from the Taskfile
• Namespaces are positioned by the smallest line number of their contained tasks, scoped to the parent Taskfile to prevent included files from altering the order
• Minor cleanup: import order in taskfile.ts, added types to tsconfig.json, added pnpm-workspace.yaml to .gitignore

Closes #230

Test plan

• Open a workspace with a Taskfile containing multiple tasks and verify the sidebar displays them in definition order
• Test with namespaces (included Taskfiles) to verify they appear at the correct position
• Test with taskfile.tree.sort set to "alphanumeric" and "none" to verify no regression
• Test with multi-root workspaces
• Verify the extension compiles and lints without errors (pnpm compile && pnpm lint)

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