fix(pin): add 'pinned' field to allowed update fields (gt-zr0a)

The 'bd pin' command was failing with "invalid field for update: pinned"
because the pinned field was missing from allowedUpdateFields.

Fixes:
- Add 'pinned' to allowedUpdateFields in queries.go
- Update importer to include pinned field in updates during import
- Add equalBool comparator for IssueDataChanged to detect pinned changes
- Fix stats query to count pinned=1 instead of status='pinned'
- Fix pinIndicator in list.go to check issue.Pinned instead of status

This unblocks gt mail --pinned functionality.

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

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

internal/importer/importer.go

@@ -554,6 +554,8 @@ func upsertIssues(ctx context.Context, sqliteStore *sqlite.SQLiteStorage, issues
 					updates["acceptance_criteria"] = incoming.AcceptanceCriteria
 					updates["notes"] = incoming.Notes
 					updates["closed_at"] = incoming.ClosedAt
+					// Pinned field (bd-7h5)
+					updates["pinned"] = incoming.Pinned
 
 					if incoming.Assignee != "" {
 						updates["assignee"] = incoming.Assignee
@@ -647,6 +649,8 @@ func upsertIssues(ctx context.Context, sqliteStore *sqlite.SQLiteStorage, issues
 				updates["acceptance_criteria"] = incoming.AcceptanceCriteria
 				updates["notes"] = incoming.Notes
 				updates["closed_at"] = incoming.ClosedAt
+				// Pinned field (bd-7h5)
+				updates["pinned"] = incoming.Pinned
 
 				if incoming.Assignee != "" {
 					updates["assignee"] = incoming.Assignee

internal/importer/utils.go

@@ -112,6 +112,15 @@ func (fc *fieldComparator) equalPriority(existing int, newVal interface{}) bool
 	return ok && int64(existing) == newPriority
 }
 
+func (fc *fieldComparator) equalBool(existingVal bool, newVal interface{}) bool {
+	switch t := newVal.(type) {
+	case bool:
+		return existingVal == t
+	default:
+		return false
+	}
+}
+
 func (fc *fieldComparator) checkFieldChanged(key string, existing *types.Issue, newVal interface{}) bool {
 	switch key {
 	case "title":
@@ -134,6 +143,8 @@ func (fc *fieldComparator) checkFieldChanged(key string, existing *types.Issue,
 		return !fc.equalStr(existing.Assignee, newVal)
 	case "external_ref":
 		return !fc.equalPtrStr(existing.ExternalRef, newVal)
+	case "pinned":
+		return !fc.equalBool(existing.Pinned, newVal)
 	default:
 		return false
 	}