[Bug]: Host grouping duplicates project groups and leaves local groups outside Local Mac

## Summary

The Projects sidebar has an incorrect group hierarchy when host grouping/filtering is enabled. Local project groups can appear outside any host section, and the same group can be duplicated under multiple hosts.

## Actual behavior

The highlighted areas in the screenshot show two problems:

- **Duplicated group:** `ob9 group` appears under both `Local Mac` and a remote Orca server. It is the same local group repeated in two host sections, making its ownership ambiguous.
- **Groups outside any host:** `tidb_dev` and `rc` appear above the `Local Mac` header, with no enclosing host section, even though they belong to `Local Mac`.

Expanding groups can reveal the duplicate group header under another host.

## Expected behavior

- `tidb_dev`, `rc`, and `ob9 group` should appear under `Local Mac`.
- Each project group should appear once under its owning host.
- Expanding or collapsing a group or host should preserve that hierarchy, including empty and collapsed groups.

## Steps to reproduce

1. Open Orca on macOS with local project groups and a remote host available.
2. Enable host grouping/filtering in the Projects sidebar so multiple host sections are visible.
3. Expand and collapse project groups and inspect their placement relative to the host headers.
4. Observe local groups above `Local Mac` and a duplicate `ob9 group` under the remote host.

## Screenshot

Red boxes highlight the groups outside any host and the duplicated `ob9 group` headers. This is an AI-edited copy of the supplied screenshot with the remote host name redacted.

## Environment

macOS; local and remote Orca hosts visible. Exact running app version not recorded.

## Related PR

Proposed fix: https://github.com/stablyai/orca/pull/19642

Start by reproducing the Projects sidebar hierarchy on macOS with local and remote hosts, then compare the behavior with the proposed fix in PR #19642. Done means each local group appears once under Local Mac, remote groups remain under their owning host, and expanding or collapsing groups preserves that hierarchy.

Written by the indexing model from the issue text.