After ao kills a runtime, the just-exited pty-host's child processes
(conpty_console_list_agent.exe, the agent's spawned shell, .git/index.lock)
still hold open handles inside the worktree for ~30 s–2 min while Windows
drains them. rmSync(force: true) deletes individual files but the parent
rmdir blocks with EBUSY/ENOTEMPTY/EPERM, leaving an empty orphan directory
under ~/.agent-orchestrator/projects/*/worktrees/.
destroy()'s catch-block fallback now calls removeDirWithRetry, which on
Windows retries with backoff [0, 100, 250, 500, 1000, 2000] ms checking
existsSync between attempts, and throws a descriptive error if the
directory survives all six. Non-Windows behaviour is unchanged (single
rmSync).
The thrown error escapes to session-manager.ts:kill which already swallows
it, so callers see no behaviour change today — but observability layers
can hook in later to surface real failures instead of silent orphans.
Addresses the Windows subset of #1562 (the cross-platform stale
.git/worktrees/<id>/ registration is still tracked there separately).
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