fix(boot-test): run every boot test with exactly what a new server gets

CI's boot test gave every blank password-like setting a throwaway value. A
real deploy only fills x-generate fields, so a template whose server won't
start without one passed CI and failed for the first owner who deployed it.

boottest-payload now fills only x-generate fields, for CI and the builder
alike. The old behaviour is kept as -fill-blank-passwords, used only by
the builder's second boot to tell whether an empty setting is why a draft
fails. Messages and AUTHORING.md no longer say boot tests fill passwords;
a server that needs a join password gets x-generate.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/gbrgames/boottest_test.go

@@ -8,7 +8,7 @@ import (
 	"testing"
 )
 
-func TestBootTestPayloadOnlyFillsBlankPasswords(t *testing.T) {
+func TestBootTestPayloadIsWhatANewServerGets(t *testing.T) {
 	dir := t.TempDir()
 	game := filepath.Join(dir, "games", "demo")
 	if err := os.MkdirAll(game, 0o755); err != nil {
@@ -52,10 +52,12 @@ configSchema:
 	if c["ENABLE_RCON"] != true {
 		t.Errorf("ENABLE_RCON changed to %v", c["ENABLE_RCON"])
 	}
-	for _, k := range []string{"RCON_PASSWORD", "ServerPassword"} {
-		if s, _ := c[k].(string); !strings.HasPrefix(s, "boot-") {
-			t.Errorf("%s not filled: %v", k, c[k])
-		}
+	// Exactly what a new server gets: the x-generate password is made, a blank join password stays blank
+	if s, _ := c["RCON_PASSWORD"].(string); !strings.HasPrefix(s, "boot-") {
+		t.Errorf("x-generate RCON_PASSWORD not filled: %v", c["RCON_PASSWORD"])
+	}
+	if c["ServerPassword"] != "" {
+		t.Errorf("ServerPassword must stay empty, as for a new server: %v", c["ServerPassword"])
 	}
 	if c["AdminPassword"] != "kept-by-owner" {
 		t.Errorf("AdminPassword overwritten: %v", c["AdminPassword"])
@@ -64,8 +66,8 @@ configSchema:
 		t.Errorf("placeholders not resolved: %v", c["MOTD"])
 	}
 
-	// As a new server gets it (what the AI builder boots): only x-generate is filled, a blank join password stays blank
-	if err := runBootTestPayload([]string{"-as-deployed", "-games", filepath.Join(dir, "games"), "-out", out, "demo"}); err != nil {
+	// Only for the builder's diagnosis: blank passwords filled too
+	if err := runBootTestPayload([]string{"-fill-blank-passwords", "-games", filepath.Join(dir, "games"), "-out", out, "demo"}); err != nil {
 		t.Fatal(err)
 	}
 	raw, _ = os.ReadFile(out)
@@ -73,10 +75,7 @@ configSchema:
 	if err := json.Unmarshal(raw, &payload); err != nil {
 		t.Fatal(err)
 	}
-	if s, _ := payload.GameConfig["RCON_PASSWORD"].(string); !strings.HasPrefix(s, "boot-") {
-		t.Errorf("as deployed: x-generate RCON_PASSWORD not filled: %v", payload.GameConfig["RCON_PASSWORD"])
-	}
-	if payload.GameConfig["ServerPassword"] != "" {
-		t.Errorf("as deployed: ServerPassword should stay empty, got %v", payload.GameConfig["ServerPassword"])
+	if s, _ := payload.GameConfig["ServerPassword"].(string); !strings.HasPrefix(s, "boot-") {
+		t.Errorf("-fill-blank-passwords: ServerPassword not filled: %v", payload.GameConfig["ServerPassword"])
 	}
 }