fix(workspaces): allow removing projects when repo folder was deleted on disk

[bilalbayram]

Summary

Fix workspace/worktree removal when repositories are deleted directly from disk (outside the app), so stale entries can still be removed from Projects.

User-visible Problem

If a parent repository folder is deleted from the filesystem and the user then tries to remove that project in CodexMonitor, removal can fail with errors like:

• Failed to remove one or more worktrees; parent workspace was not removed.
• Failed to run git: No such file or directory (os error 2)

This leaves stale project/worktree entries in the app.

Root Cause

remove_workspace_core and remove_worktree_core attempted git worktree commands unconditionally when the child worktree path existed.

Those commands run with current_dir set to the parent repo path. When the parent directory has already been deleted, process spawn fails at the OS level (os error 2) before git can return a normal semantic worktree error.

Because that OS error does not match is_missing_worktree_error, the removal flow treated it as a hard failure (or accumulated child failures), and parent workspace deletion could be blocked.

What Changed

1. remove_workspace_core now checks whether the parent repo path exists as a directory.
2. If the parent repo path is missing:

• Skip git worktree remove calls.
• Remove child worktree directories directly via filesystem cleanup.
• Skip git worktree prune.

3. remove_worktree_core now applies the same missing-parent-path behavior for single worktree removal.
4. Existing behavior is preserved when the parent repo path exists: git-based removal/prune still runs as before.

Why This Is Safe

• No contract/API changes in Tauri or daemon RPC surfaces.
• No changes to workspace/worktree IDs, persistence schema, or payload shapes.
• Logic only diverges in a failure-path condition (missing parent repo directory).
• Normal in-repo removal path remains unchanged.

Regression Tests Added

Added tests in src-tauri/src/workspaces/tests.rs:

• remove_workspace_succeeds_when_parent_repo_folder_is_missing
• remove_worktree_succeeds_when_parent_repo_folder_is_missing

Both tests assert:

• Removal succeeds when parent repo path is absent.
• Filesystem worktree folder is cleaned up.
• In-memory workspace map is updated correctly.
• Git command path is not invoked in this missing-parent scenario.

Validation

Executed:

• cargo test --manifest-path src-tauri/Cargo.toml remove_workspace_succeeds_when_parent_repo_folder_is_missing
• cargo test --manifest-path src-tauri/Cargo.toml remove_worktree_succeeds_when_parent_repo_folder_is_missing
• cargo check --manifest-path src-tauri/Cargo.toml
• npm run typecheck

All passed.

Files Changed

• src-tauri/src/shared/workspaces_core/crud_persistence.rs
• src-tauri/src/shared/workspaces_core/worktree.rs
• src-tauri/src/workspaces/tests.rs

[bilalbayram]

Superseded by upstream PR: Dimillian#421