* fix(win): taskkill agent PTY descendant trees on stop
Windows agent teardown previously degraded to shell-only kill because
descendant snapshot is POSIX-only. Orphaned claude/codex/MCP children
kept worktree cwd handles open and blocked worktree remove.
Use taskkill /T /F on the PTY root in killWithDescendantSweep (daemon +
local agent shutdown) so the ConPTY tree is cleared before teardown.
Fixes#10004
* fix(win): bound taskkill with timeout and windowsHide
Prevent a wedged taskkill from delaying killRoot, and hide the console
flash during agent PTY tree teardown (CodeRabbit on #10100).
