feat(desktop): make Projects workspaces selectable (#6368)

## Summary

Projects workspaces now support consistent selection across projects,
repositories, reviews, tasks, and channel results. A user can collect
related entities, see the active selection without losing their current
workspace, and pass a bounded, injection-safe representation to an agent
for discussion.

Detail views now keep repository source and availability explicit while
preserving contextual actions across local and remote workspaces.
Missing or inaccessible repositories produce a recoverable state instead
of leaving the workspace ambiguous.

This is part 2 of the Projects v6 stack. Parts 3 and 4 will add
context-aware collaboration and navigation/detail-page polish.

### Related issue

Related: #6335

### Testing

- Full pre-push gate passed: file-size checks, Biome, TypeScript,
Desktop unit tests, Tauri checks, and Rust tests
- Project context safety suite: 9/9 passed, including bounded untrusted
overview data and hidden-context stripping
- Updated Playwright coverage exercises grouped selection,
selection-aware agent context, repository source states, and detail
actions

---------

Signed-off-by: Thomas Petersen <thomasp@squareup.com>

desktop/src/shared/api/projectGit.ts

@@ -354,6 +354,18 @@ export async function getProjectRepoSyncStatus(input: {
   return fromRawProjectRepoSyncStatus(status);
 }
 
+export async function openProjectRepositoryFolder(input: {
+  reposDir?: string | null;
+  projectDtag: string;
+  cloneUrl: string;
+}): Promise<void> {
+  await invokeTauri("open_project_repository_folder", {
+    reposDir: input.reposDir ?? null,
+    projectDtag: input.projectDtag,
+    cloneUrl: input.cloneUrl,
+  });
+}
+
 type RawProjectTerminalResult = {
   path: string;
   cloned: boolean;