## Objective

Let projects add inclusion patterns without repeating defaults or
patterns inherited from user settings.

Part of #64399.

## Solution

Extend the `"..."` behavior from #62769 and #64222 to
`file_scan_inclusions` using the shared merge implementation. `"..."`
includes the resolved inherited list, omitting it replaces the list, and
`[]` clears it. Duplicate entries retain their first occurrence.

Stop importing VS Code’s `files.watcherInclude` as inclusion patterns
because it configures additional watch roots rather than overriding Git
ignores.

## Testing

Tested on macOS with settings merge, VS Code import, and worktree
integration tests. Coverage includes preservation of the `.env*`
default, layered inheritance, replacement, clearing, and deduplication.
The worktree test verifies that inherited and project-specific patterns
include Git-ignored files while exclusions still take precedence.

To check manually, configure different user and project inclusion
patterns and add ignored files matching each. Include `"..."` to retain
inherited patterns, then repeat without it and with `[]` to verify
replacement and clearing. Confirm that excluded files remain absent.

## Self-Review Checklist:

- [x] I’ve reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed’s UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

---

Release Notes:

- Added support for `"..."` in `file_scan_inclusions` so project
settings can extend inherited inclusion patterns.