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.

cmd/jobsearch/main.go

@@ -27,7 +27,6 @@ import (
 
 	"git.avsdev.uk/Go/job-search/internal/cli"
 	"git.avsdev.uk/Go/job-search/internal/cli/config"
-	"git.avsdev.uk/Go/job-search/internal/cli/fetch"
 	"git.avsdev.uk/Go/job-search/internal/cli/migrate"
 	"git.avsdev.uk/Go/job-search/internal/cli/serve"
 	"git.avsdev.uk/Go/job-search/internal/cli/version"
@@ -74,7 +73,6 @@ opportunities.
 	root.AddCommand(
 		version.NewCommand(),
 		config.NewCommand(opts),
-		fetch.NewCommand(opts),
 		migrate.NewCommand(opts),
 		serve.NewCommand(opts),
 	)

cmd/jobsearch/main_test.go

@@ -18,7 +18,7 @@ func TestCommandTree(t *testing.T) {
 		names = append(names, c.Name())
 	}
 
-	commands := []string{"config", "fetch", "migrate", "serve", "version"}
+	commands := []string{"config", "migrate", "serve", "version"}
 	for _, want := range commands {
 		if !slices.Contains(names, want) {
 			t.Errorf("job-search has no %q command; has %v", want, names)