fix(actions): keep action run title clickable when commit subject is a URL (#37867)

- When a commit subject is a bare URL, `linkProcessor` wrapped it in its
own `<a>` to that URL. Because HTML cannot nest anchors, the wrapping
default link (the action run / commit link) was lost and the action
title became unclickable — clicking it sent the user to the URL from the
commit message instead of the action log.
- Drop `linkProcessor` from `PostProcessCommitMessageSubject` so the
whole subject stays wrapped in the default link. URLs in subjects now
render as text inside that link; URLs in commit bodies are unaffected.

Fixes #37865

---------

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

modules/markup/html.go

@@ -175,16 +175,25 @@ var emojiProcessors = []processor{
 	emojiProcessor,
 }
 
+// isBareURLSubject reports whether the (HTML-escaped) commit subject content
+// is entirely a single URL, ignoring leading/trailing whitespace.
+func isBareURLSubject(content string) bool {
+	s := strings.TrimSpace(html.UnescapeString(content))
+	if s == "" {
+		return false
+	}
+	m := common.GlobalVars().LinkRegex.FindStringIndex(s)
+	return m != nil && m[0] == 0 && m[1] == len(s)
+}
+
 // PostProcessCommitMessageSubject will use the same logic as PostProcess and
 // PostProcessCommitMessage, but will disable the shortLinkProcessor and
-// emailAddressProcessor, will add a defaultLinkProcessor if defaultLink is set,
-// which changes every text node into a link to the passed default link.
+// emailAddressProcessor, and wraps the whole subject in defaultLink.
 func PostProcessCommitMessageSubject(ctx *RenderContext, defaultLink, content string) (string, error) {
 	procs := []processor{
 		fullIssuePatternProcessor,
 		comparePatternProcessor,
 		fullHashPatternProcessor,
-		linkProcessor,
 		mentionProcessor,
 		issueIndexPatternProcessor,
 		commitCrossReferencePatternProcessor,
@@ -192,6 +201,15 @@ func PostProcessCommitMessageSubject(ctx *RenderContext, defaultLink, content st
 		emojiShortCodeProcessor,
 		emojiProcessor,
 	}
+	// When the whole subject is a bare URL, linkProcessor would turn it into
+	// a competing anchor and hijack the surrounding defaultLink wrapper, leaving
+	// the subject visually unclickable. Match GitHub: render such subjects as
+	// plain text inside defaultLink. Partial URLs inside larger text still become
+	// their own links (nested anchors aren't legal HTML, so the outer defaultLink
+	// naturally breaks on that span, same as on GitHub).
+	if !isBareURLSubject(content) {
+		procs = append(procs, linkProcessor)
+	}
 	procs = append(procs, func(ctx *RenderContext, node *html.Node) {
 		ch := &html.Node{Parent: node, Type: html.TextNode, Data: node.Data}
 		node.Type = html.ElementNode