Split fetch from jobsearch into a separate fetcher command, and renamed fetch once to fts-once

job-search no longer has a fetch command. Its subcommands are now in
cmd/fetcher, which reads the same configuration: "fetcher service" runs
every enabled source's fetcher on its interval until stopped, and
"fetcher fts-once" (was "fetch once") fetches from Find a Tender once and
prints the releases as JSON. The new namea say what the commands do,
because service runs every source while fts-once fetches only from Find a
Tender.

The code stays in internal/cli/fetch, where NewCommands replaces the fetch
parent command. once.go is now fts_once.go and commandOnce is
commandFTSOnce. The README's usage, the config README and the find_a_tender
api_root comment now give the new command names.

internal/cli/fetch/command.go

@@ -1,29 +1,18 @@
+// Package fetch holds the fetcher commands: "fts-once" fetches from Find a
+// Tender once and prints the releases, and "service" polls every enabled
+// source on its interval.
 package fetch
 
 import (
-	"log/slog"
-
 	"github.com/spf13/cobra"
 
 	"git.avsdev.uk/Go/job-search/internal/cli"
 )
 
-// NewCommand returns the "fetch" command, which fetches opportunities once or
-// as a service.
-func NewCommand(opts *cli.Options) *cobra.Command {
-	cmd := &cobra.Command{
-		Use:   "fetch",
-		Short: "Fetch current opportunities",
-		PersistentPreRun: func(cmd *cobra.Command, args []string) {
-			slog.Debug("command persistent pre-run", "command", "fetch")
-		},
-		PersistentPostRun: func(cmd *cobra.Command, args []string) {
-			slog.Debug("command persistent post-run", "command", "fetch")
-		},
+// NewCommands returns the fetcher commands, "fts-once" and "service".
+func NewCommands(opts *cli.Options) []*cobra.Command {
+	return []*cobra.Command{
+		commandFTSOnce(opts),
+		commandService(opts),
 	}
-
-	cmd.AddCommand(commandOnce(opts))
-	cmd.AddCommand(commandService(opts))
-
-	return cmd
 }