[Bug]: Storage cleanup never removes worktrees in ~/.t3/worktrees that no thread owns, so agent-created worktrees pile up #25843

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/server

Steps to reproduce

1. Turn storage cleanup on (worktreeAfterDays: 7, worktreeSettledAfterDays: 2, worktreeOnMerge, worktreeOnDelete and worktreeUnchanged all on).
2. In a thread, let the agent create its own worktree inside T3's worktrees folder, for example git -C <project> worktree add ~/.t3/worktrees/<project>/review-123 -b review-123. Agents do this often when they want a second checkout for a review or a PR push.
3. Finish the work, push the branch, and leave the worktree clean.
4. Wait more than 7 days, or run storage cleanup by hand.

Expected behavior

A clean worktree under ~/.t3/worktrees/ whose commits are on a remote, and which no thread uses, is removed by cleanup with the same safety checks as thread worktrees. At minimum, the storage panel offers a way to remove it.

Actual behavior

The storage report lists it as "No thread uses this worktree", but cleanup never removes it. In the trace, StorageCleanup.sweep → cleanWorktrees → reportOrphanWorktrees succeeds on every run. The only "storage cleanup removed worktree" events are for worktrees with a threadId.

On one machine this left 81 orphaned worktrees in the report, from 0 to 14 days old (24 of them older than the 7-day setting). None used T3's t3-<id> naming, so all were created by agents. Across the whole folder there were about 194 registered worktrees, about 150 of them agent-named, and the disk reached 97% full.

Impact

Major degradation or frequent failure

Version or commit

0.1.3-nightly.20261027.3754

Environment

Ubuntu, Linux 7.0, desktop app. Claude and Codex providers, many delegated tasks.

Workaround

Remove them by hand: for each worktree with an empty git status --porcelain whose HEAD shows up in git branch -r --contains, run git worktree remove.