fix: race condition in reporter between RunDaemon and Close (#796)

## Summary

- Fix data race on `r.closed` between `RunDaemon()` and `Close()` by protecting it with the existing `stateMu` — `closed` is part of the reporter state. `RunDaemon()` reads it under `stateMu.RLock()`, `Close()` sets it inside the existing `stateMu.Lock()` block
- `ReportState` now has a parameter to not report results from runDaemon even if set, from now on `Close` reports the result
- `Close` waits for `RunDaemon()` to signal exit via a closed channel `daemon` before reporting the final logs and state with result, unless something really wrong happens it does not time out
- Add `TestReporter_EphemeralRunnerDeletion` which reproduces the exact scenario from #793: RunDaemon's `ReportState` racing with `Close`, causing the ephemeral runner to be deleted before final logs are sent
- Add `TestReporter_RunDaemonClose_Race` which exercises `RunDaemon()` and `Close()` concurrently to verify no data race on `r.closed` under `go test -race`
- Enable `-race` flag in `make test` so CI catches data races going forward

Based on #794, with fixes for the remaining unprotected `r.closed` reads that the race detector catches.

Fixes #793

---------

Co-authored-by: Christopher Homberger <christopher.homberger@web.de>
Co-authored-by: ChristopherHX <christopher.homberger@web.de>
Co-authored-by: rmawatson <rmawatson@hotmail.com>
Reviewed-on: https://gitea.com/gitea/act_runner/pulls/796
Reviewed-by: ChristopherHX <christopherhx@noreply.gitea.com>
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

Makefile

@@ -125,7 +125,7 @@ tidy-check: tidy
 	fi
 
 test: fmt-check security-check
-	@$(GO) test -v -cover -coverprofile coverage.txt ./... && echo "\n==>\033[32m Ok\033[m\n" || exit 1
+	@$(GO) test -race -v -cover -coverprofile coverage.txt ./... && echo "\n==>\033[32m Ok\033[m\n" || exit 1
 
 .PHONY: vet
 vet: