refactor: unify export path logic and default to Downloads

[hannesrudolph]

Summary

Standardized the file export logic across Settings, Modes, Tasks, and Images. All exports now default to the Downloads folder (when no history exists) and remember the last used location.

Changes

• Created `src/utils/export.ts` with `resolveDefaultSaveUri` helper
• Updated Settings export to default to Downloads (was Documents)
• Updated Mode export to fallback to Downloads (was home)
• Updated Task/Image export to explicitly use Downloads
• Removed duplicated path logic from integration handlers

---

Important

Refactors export path logic to standardize default export directories and remember last used paths across various components.

• Behavior:
  • Standardizes export paths to default to Downloads if no history exists, across Settings, Modes, Tasks, and Images.
  • Remembers last used export location for subsequent exports.
• Code Changes:
  • Introduces resolveDefaultSaveUri in export.ts to determine default save paths.
  • Updates exportSettings in importExport.ts to use resolveDefaultSaveUri.
  • Modifies exportTaskWithId in ClineProvider.ts to use resolveDefaultSaveUri.
  • Adjusts saveImage in image-handler.ts to use resolveDefaultSaveUri.
• Misc:
  • Removes redundant path logic from integration handlers.

^{This description was created by for e53c0e0. You can customize this summary. It will automatically update as commits are pushed.}

[roomote]

Oroocle   Follow along on Roo Cloud

Reviewed latest changes. No remaining issues.

• Consider making resolveDefaultSaveUri non-async to avoid require-await linting and clarify the API.

Previous reviews

• e53c0e0: Review #1
• c25d8cc: Review #2

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}