test(sidebar): harden #8865 project-group sleep-filter coverage

Add adversarial cases for explicit project filters, multi-member groups,
ungrouped neighbors, and buildRows membership/count preservation.

Co-authored-by: bbingz <zzb@gxsmjx.com>

src/renderer/src/components/sidebar/empty-project-placeholder-repos.test.ts

@@ -131,4 +131,72 @@ describe('getEmptyProjectPlaceholderRepoIds', () => {
       }).size
     ).toBe(0)
   })
+
+  it('still respects explicit project filters for sleep-filtered grouped members', () => {
+    const selected: Repo = { ...repo, id: 'repo-selected', projectGroupId: 'group-1' }
+    const filteredOut: Repo = { ...repo, id: 'repo-hidden', projectGroupId: 'group-1' }
+    const selectedWt: Worktree = { ...worktree, id: 'wt-selected', repoId: selected.id }
+    const hiddenWt: Worktree = { ...worktree, id: 'wt-hidden', repoId: filteredOut.id }
+
+    expect(
+      Array.from(
+        getEmptyProjectPlaceholderRepoIds({
+          groupBy: 'repo',
+          repos: [selected, filteredOut],
+          worktreesByRepo: {
+            [selected.id]: [selectedWt],
+            [filteredOut.id]: [hiddenWt]
+          },
+          // Why: simulate Hide sleeping removing every card while the project
+          // filter still intentionally excludes `filteredOut`.
+          visibleWorktrees: [],
+          filterRepoIds: [selected.id]
+        })
+      )
+    ).toEqual([selected.id])
+  })
+
+  it('placeholders only the fully-filtered members of a multi-project group', () => {
+    const sleeping: Repo = { ...repo, id: 'repo-sleeping', projectGroupId: 'group-1' }
+    const awake: Repo = { ...repo, id: 'repo-awake', projectGroupId: 'group-1' }
+    const sleepingWt: Worktree = { ...worktree, id: 'wt-sleeping', repoId: sleeping.id }
+    const awakeWt: Worktree = { ...worktree, id: 'wt-awake', repoId: awake.id }
+
+    expect(
+      Array.from(
+        getEmptyProjectPlaceholderRepoIds({
+          groupBy: 'repo',
+          repos: [sleeping, awake],
+          worktreesByRepo: {
+            [sleeping.id]: [sleepingWt],
+            [awake.id]: [awakeWt]
+          },
+          visibleWorktrees: [awakeWt],
+          filterRepoIds: []
+        })
+      )
+    ).toEqual([sleeping.id])
+  })
+
+  it('does not placeholder ungrouped neighbors of a filtered grouped member', () => {
+    const grouped: Repo = { ...repo, id: 'repo-grouped', projectGroupId: 'group-1' }
+    const ungrouped: Repo = { ...repo, id: 'repo-ungrouped' }
+    const groupedWt: Worktree = { ...worktree, id: 'wt-grouped', repoId: grouped.id }
+    const ungroupedWt: Worktree = { ...worktree, id: 'wt-ungrouped', repoId: ungrouped.id }
+
+    expect(
+      Array.from(
+        getEmptyProjectPlaceholderRepoIds({
+          groupBy: 'repo',
+          repos: [grouped, ungrouped],
+          worktreesByRepo: {
+            [grouped.id]: [groupedWt],
+            [ungrouped.id]: [ungroupedWt]
+          },
+          visibleWorktrees: [],
+          filterRepoIds: []
+        })
+      )
+    ).toEqual([grouped.id])
+  })
 })

src/renderer/src/components/sidebar/worktree-list-groups.test.ts

@@ -1933,6 +1933,73 @@ describe('project groups', () => {
     expect(rows[0]).toMatchObject({ label: 'Platform' })
   })
 
+  it('keeps sleep-filtered Project Group members as empty project headers', () => {
+    // Why: #8865 — Hide sleeping removes workspace cards; membership placeholders
+    // must still project the grouped project header so the group count stays honest.
+    const group: ProjectGroup = {
+      id: 'group-1',
+      name: 'Platform',
+      parentPath: '/platform',
+      parentGroupId: null,
+      createdFrom: 'folder-scan',
+      tabOrder: 0,
+      isCollapsed: false,
+      color: null,
+      createdAt: 1,
+      updatedAt: 1
+    }
+    const sleepingRepo: Repo = {
+      ...repo,
+      id: 'repo-sleeping',
+      displayName: 'sleeping-project',
+      projectGroupId: group.id
+    }
+    const awakeRepo: Repo = {
+      ...repo,
+      id: 'repo-awake',
+      displayName: 'awake-project',
+      projectGroupId: group.id
+    }
+    const awakeWorktree: Worktree = {
+      ...worktree,
+      id: 'wt-awake',
+      repoId: awakeRepo.id,
+      path: '/tmp/awake'
+    }
+
+    const rows = buildRows(
+      'repo',
+      [awakeWorktree],
+      new Map([
+        [sleepingRepo.id, sleepingRepo],
+        [awakeRepo.id, awakeRepo]
+      ]),
+      null,
+      new Set(),
+      undefined,
+      undefined,
+      undefined,
+      {},
+      new Map([[awakeWorktree.id, awakeWorktree]]),
+      false,
+      undefined,
+      [group],
+      new Set([sleepingRepo.id])
+    )
+
+    expect(rows[0]).toMatchObject({
+      type: 'header',
+      key: 'project-group:group-1',
+      count: 2
+    })
+    // Why: empty/placeholder projects sort after projects with visible activity.
+    expect(rows.filter((row) => row.type === 'header').map((row) => row.key)).toEqual([
+      'project-group:group-1',
+      `repo:${awakeRepo.id}`,
+      `repo:${sleepingRepo.id}`
+    ])
+  })
+
   it('renders ungrouped repos as top-level repo rows when Project Groups exist', () => {
     const group: ProjectGroup = {
       id: 'group-1',