fix: deliver cancel ack and reap leftover Windows job processes (#996)

## Summary

- When Gitea cancels a job, the reporter cancels its own task context; the final Close() flush then aborted on that same cancelled context and Gitea never received the runner's acknowledgement (missing tail logs and final state).
- On Windows the cancelled context also neutralised terminateRunningProcesses, leaving step grandchildren alive in the workspace, holding file handles, so the runner could no longer clean up and pick up new work.
- Reporter.Close() now flushes on a detached, bounded context via a new rpcCtx() helper and configurable Runner.ReportCloseTimeout (default 10s).
- terminateRunningProcesses now PowerShell-enumerates Win32_Process and taskkill /T /F's every process whose ExecutablePath or CommandLine references the job's workspace directories, on a detached context.
- The daemon heartbeat loop still exits on <-r.ctx.Done(): the runner is intentionally seen as offline by Gitea during cleanup so it isn't handed a new task overlapping the in-progress teardown.

## Test plan

- [x] go test ./internal/pkg/report/... ./act/container/ -run 'TestReporter_ServerCancelStillFlushesFinal|TestBuildWindowsWorkspaceKillScript'
- [x] make fmt && make lint-go - 0 issues
- [x] GOOS=windows go build ./... - clean
- [x] Manual on a Windows runner: trigger a long-running workflow, cancel from Gitea UI; verify (a) the job ends with tail logs + cancelled state in Gitea, (b) workspace cleans up, (c) the runner picks up a new job without restart.

Authored-by: bircni
🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: silverwind <me@silverwind.io>
Reviewed-on: https://gitea.com/gitea/runner/pulls/996
Reviewed-by: silverwind <2021+silverwind@noreply.gitea.com>

internal/pkg/config/config.go

@@ -39,6 +39,7 @@ type Runner struct {
 	LogReportMaxLatency time.Duration     `yaml:"log_report_max_latency"` // LogReportMaxLatency specifies the max time a log row can wait before being sent.
 	LogReportBatchSize  int               `yaml:"log_report_batch_size"`  // LogReportBatchSize triggers immediate log flush when buffer reaches this size.
 	StateReportInterval time.Duration     `yaml:"state_report_interval"`  // StateReportInterval specifies the interval for state reporting.
+	ReportCloseTimeout  time.Duration     `yaml:"report_close_timeout"`   // ReportCloseTimeout caps each RPC attempt when flushing the final logs and task state at job completion, on a detached context so a server cancel can't block the acknowledgement.
 	Labels              []string          `yaml:"labels"`                 // Labels specify the labels of the runner. Labels are declared on each startup
 	GithubMirror        string            `yaml:"github_mirror"`          // GithubMirror defines what mirrors should be used when using github
 	AllocatePTY         bool              `yaml:"allocate_pty"`           // AllocatePTY allocates a pseudo-TTY for each step's process. Default is false, matching GitHub's actions/runner. Enable only for jobs that need an interactive terminal; tools like docker build emit redrawing progress frames into the captured log when a TTY is present. Applies to both host and docker backends.
@@ -183,6 +184,9 @@ func LoadDefault(file string) (*Config, error) {
 	if cfg.Runner.StateReportInterval <= 0 {
 		cfg.Runner.StateReportInterval = 5 * time.Second
 	}
+	if cfg.Runner.ReportCloseTimeout <= 0 {
+		cfg.Runner.ReportCloseTimeout = 10 * time.Second
+	}
 	if cfg.Metrics.Addr == "" {
 		cfg.Metrics.Addr = "127.0.0.1:9101"
 	}