feat(list): Add type aliases for --type flag (gt-pvhsv)

Add convenience aliases for common type names:
- mr → merge-request
- feat → feature
- mol → molecule

Applied to bd list, bd ready, and bd export commands.
Case-insensitive matching (MR, Mr, mr all work).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/util/strings.go

@@ -2,6 +2,23 @@ package util
 
 import "strings"
 
+// issueTypeAliases maps shorthand type names to canonical types
+var issueTypeAliases = map[string]string{
+	"mr":   "merge-request",
+	"feat": "feature",
+	"mol":  "molecule",
+}
+
+// NormalizeIssueType expands type aliases to their canonical forms.
+// For example: "mr" -> "merge-request", "feat" -> "feature", "mol" -> "molecule"
+// Returns the input unchanged if it's not an alias.
+func NormalizeIssueType(t string) string {
+	if canonical, ok := issueTypeAliases[strings.ToLower(t)]; ok {
+		return canonical
+	}
+	return t
+}
+
 // NormalizeLabels trims whitespace, removes empty strings, and deduplicates labels
 // while preserving order.
 func NormalizeLabels(ss []string) []string {