browserrot(gitea): fix login submit selector from live read-only inspection

Read-only GET of a live Gitea /user/login showed the sign-in button is
<button class="ui primary button"> with NO type=submit attribute, so the seed
".ui.primary.button[type=submit]" would miss. Corrected to ".ui.primary.button"
(the mobile navbar toggle lacks "primary", so it stays unambiguous). Confirmed
during M-B4 rung-1 pre-live-fire prep; change-form selectors remain auth-gated
and self-heal-covered until the live run.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/browserrot/sites.go

@@ -38,10 +38,14 @@ func GiteaSite(baseURL, username string) Site {
 			SuccessText: "has been updated",
 		},
 		Login: Login{
-			URL:       base + "/user/login",
-			UserSel:   "#user_name",
-			PassSel:   "#password",
-			SubmitSel: ".ui.primary.button[type=submit], button[type=submit]",
+			URL:     base + "/user/login",
+			UserSel: "#user_name",
+			PassSel: "#password",
+			// Gitea's sign-in button is <button class="ui primary button"> with NO
+			// type=submit attribute (confirmed by read-only inspection of a live
+			// instance 2026-07-20) — it submits as the form's only button. The mobile
+			// #navbar-expand-toggle button lacks "primary", so this stays unambiguous.
+			SubmitSel: ".ui.primary.button",
 			// Post-login, Gitea lands on the dashboard. The sign-out control's text is a
 			// stable "logged in" marker across themes; confirm on first run.
 			SuccessSel:  "body",