Rename act_runner to runner (#850)

## Consumer-facing breaking changes

- **Go module path**: `gitea.com/gitea/act_runner` → `gitea.com/gitea/runner`. Anything importing `act/...` or `internal/...` packages (notably Gitea itself) must update imports.
- **Binary name**: `act_runner` → `gitea-runner`. Wrapper scripts, systemd units, init scripts, and documentation referencing the binary by `act_runner` will break.
- **Docker image**: `gitea/act_runner` → `gitea/runner` (incl. `*-dind-rootless` variants). Users pulling `gitea/act_runner:nightly` etc. will get stale images. Note: the image name is `gitea/runner`, not `gitea/gitea-runner`.
- **Release artifact paths**: S3 directory `act_runner/{{.Version}}` → `gitea-runner/{{.Version}}`, and artifact filenames change with the new project name. Existing download URLs break.
- **Metrics namespace**: changed from `act_runner` to `gitea_runner` (e.g. `act_runner_jobs_total` → `gitea_runner_jobs_total`); existing monitors/dashboards must be updated.
- **ldflags version path**: `gitea.com/gitea/act_runner/internal/pkg/ver.version` → `gitea.com/gitea/runner/internal/pkg/ver.version`. Affects anyone building with custom ldflags.
- **Kubernetes example resource names**: `act-runner` / `act-runner-vol` → `runner` / `runner-vol`. Users who copied the manifests verbatim will see resource churn on apply.
- **s6 service name**: `scripts/s6/act_runner/` → `scripts/s6/gitea-runner/` (image-internal; only matters for downstream image overrides).

Unchanged: YAML config field names, env vars (`GITEA_*`), CLI flags/subcommands, registration file format.
---------

Co-authored-by: silverwind <me@silverwind.io>
Reviewed-on: https://gitea.com/gitea/runner/pulls/850
Reviewed-by: Zettat123 <39446+zettat123@noreply.gitea.com>
Reviewed-by: silverwind <2021+silverwind@noreply.gitea.com>
Reviewed-by: Nicolas <bircni@icloud.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-committed-by: Lunny Xiao <xiaolunwen@gmail.com>

internal/app/cmd/cmd.go

@@ -8,25 +8,24 @@ import (
 	"fmt"
 	"os"
 
-	"gitea.com/gitea/act_runner/internal/pkg/config"
-	"gitea.com/gitea/act_runner/internal/pkg/ver"
+	"gitea.com/gitea/runner/internal/pkg/config"
+	"gitea.com/gitea/runner/internal/pkg/ver"
 
 	"github.com/spf13/cobra"
 )
 
 func Execute(ctx context.Context) {
-	// ./act_runner
+	// ./gitea-runner
 	rootCmd := &cobra.Command{
-		Use:          "act_runner [event name to run]\nIf no event name passed, will default to \"on: push\"",
-		Short:        "Run GitHub actions locally by specifying the event name (e.g. `push`) or an action name directly.",
-		Args:         cobra.MaximumNArgs(1),
+		Use:          "gitea-runner",
+		Short:        "Gitea Runner",
 		Version:      ver.Version(),
 		SilenceUsage: true,
 	}
 	configFile := ""
 	rootCmd.PersistentFlags().StringVarP(&configFile, "config", "c", "", "Config file path")
 
-	// ./act_runner register
+	// ./gitea-runner register
 	var regArgs registerArgs
 	registerCmd := &cobra.Command{
 		Use:   "register",
@@ -42,7 +41,7 @@ func Execute(ctx context.Context) {
 	registerCmd.Flags().BoolVar(&regArgs.Ephemeral, "ephemeral", false, "Configure the runner to be ephemeral and only ever be able to pick a single job (stricter than --once)")
 	rootCmd.AddCommand(registerCmd)
 
-	// ./act_runner daemon
+	// ./gitea-runner daemon
 	var daemArgs daemonArgs
 	daemonCmd := &cobra.Command{
 		Use:   "daemon",
@@ -53,10 +52,10 @@ func Execute(ctx context.Context) {
 	daemonCmd.Flags().BoolVar(&daemArgs.Once, "once", false, "Run one job then exit")
 	rootCmd.AddCommand(daemonCmd)
 
-	// ./act_runner exec
+	// ./gitea-runner exec
 	rootCmd.AddCommand(loadExecCmd(ctx))
 
-	// ./act_runner config
+	// ./gitea-runner config
 	rootCmd.AddCommand(&cobra.Command{
 		Use:   "generate-config",
 		Short: "Generate an example config file",
@@ -66,7 +65,7 @@ func Execute(ctx context.Context) {
 		},
 	})
 
-	// ./act_runner cache-server
+	// ./gitea-runner cache-server
 	var cacheArgs cacheServerArgs
 	cacheCmd := &cobra.Command{
 		Use:   "cache-server",