fix: resolve git authors to GitHub usernames in release notes (#3)

## Summary
- Extract GitHub usernames from noreply email addresses in git commits
- Format contributors as @username links in release notes
- Works for both AI-generated and git fallback release notes

## Test plan
- [ ] Verify `go test ./...` passes
- [ ] Trigger a release and check contributors section shows @username
links

Author: machado144

domain/types.go

@@ -9,6 +9,7 @@ type DetailedCommit struct {
 	Hash         string   `json:"hash"`
 	Message      string   `json:"message"`
 	Author       string   `json:"author"`
+	AuthorEmail  string   `json:"author_email"`
 	Date         string   `json:"date"`
 	FilesChanged []string `json:"files_changed"`
 	FileCount    int      `json:"file_count"`

services/git.go

@@ -128,12 +128,20 @@ func (g *GitService) GetCommitDetails(commits []domain.CommitInfo) ([]domain.Det
 			Message: c.Message,
 		}
 
-		// Get author and date
+		// Get author name, email, and date
 		authorOut, err := g.runGit("show", c.Hash, "--format=%an", "--no-patch")
 		if err == nil {
 			dc.Author = strings.TrimSpace(authorOut)
 		}
 
+		emailOut, err := g.runGit("show", c.Hash, "--format=%ae", "--no-patch")
+		if err == nil {
+			dc.AuthorEmail = strings.TrimSpace(emailOut)
+			if ghUser := extractGitHubUser(dc.AuthorEmail); ghUser != "" {
+				dc.Author = "@" + ghUser
+			}
+		}
+
 		dateOut, err := g.runGit("show", c.Hash, "--format=%ci", "--no-patch")
 		if err == nil {
 			dc.Date = strings.TrimSpace(dateOut)
@@ -273,6 +281,18 @@ func (g *GitService) touchesIgnored(files, ignoreList []string) bool {
 	return false
 }
 
+func extractGitHubUser(email string) string {
+	if !strings.HasSuffix(email, "@users.noreply.github.com") {
+		return ""
+	}
+	local := strings.TrimSuffix(email, "@users.noreply.github.com")
+	// Handle id+username format (e.g. 12345+username@users.noreply.github.com)
+	if idx := strings.Index(local, "+"); idx >= 0 {
+		return local[idx+1:]
+	}
+	return local
+}
+
 func splitLines(s string) []string {
 	var lines []string
 	for _, line := range strings.Split(s, "\n") {

services/prompt.go

@@ -380,7 +380,11 @@ func (p *PromptService) GenerateGitFallbackNotes(
 		authors := uniqueAuthors(detailedCommits)
 		if len(authors) > 0 {
 			for _, a := range authors {
-				notes.WriteString(fmt.Sprintf("- %s\n", a))
+				if strings.HasPrefix(a, "@") {
+					notes.WriteString(fmt.Sprintf("- [%s](https://github.com/%s)\n", a, a[1:]))
+				} else {
+					notes.WriteString(fmt.Sprintf("- %s\n", a))
+				}
 			}
 		} else {
 			notes.WriteString("- N/A\n")