fix(host): correct host workspace cleanup on Windows (#883)

## Summary
- Fix host-mode cleanup to remove the job **workspace** directory after a run (instead of leaving checkouts behind).
- On Windows, track step process PIDs and terminate remaining process trees during teardown before attempting workspace deletion (prevents file-lock failures).
- Skip workspace deletion when `bind_workdir` is enabled to avoid conflicting with runner-level task directory cleanup.

## Implementation details
- `HostEnvironment` now records PIDs for started commands and best-effort terminates them on Windows during `Remove()`.
- Workspace removal uses a small retry loop on Windows to handle transient locks.
- `BindWorkdir` is propagated into `HostEnvironment` so cleanup behavior matches runner configuration.

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: silverwind <2021+silverwind@noreply.gitea.com>
Reviewed-on: https://gitea.com/gitea/runner/pulls/883
Reviewed-by: silverwind <2021+silverwind@noreply.gitea.com>

internal/app/run/runner.go

@@ -12,6 +12,7 @@ import (
 	"net/http"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -238,6 +239,13 @@ func (r *Runner) run(ctx context.Context, task *runnerv1.Task, reporter *report.
 		workdirParent = fmt.Sprintf("%s/%d", workdirParent, task.Id)
 	}
 	workdir := filepath.FromSlash(fmt.Sprintf("/%s/%s", workdirParent, preset.Repository))
+	if runtime.GOOS == "windows" {
+		if abs, err := filepath.Abs(workdir); err == nil {
+			workdir = abs
+		}
+	}
+	// Without bind_workdir, the workspace path omits the task id; concurrent host-mode jobs
+	// for the same repository would share this directory and can race with per-job cleanup.
 
 	runnerConfig := &runner.Config{
 		// On Linux, Workdir will be like "/<parent_directory>/<owner>/<repo>"