feat(mcp): Prefab UI parity for the 3 remaining mutations (#46)

Brings add_order_comment, update_order_due_date, and bulk_update_order_status into the find/view/decide/mutate Prefab UI cluster from #20. Each gets:
- Typed Pydantic preview schema (CommentPreview / DueDateChangePreview / BulkStatusChangePreview) replacing the ad-hoc dict[str, Any] previews
- Typed Pydantic result schema with confirmed: bool to accurately represent the user-declined elicitation path
- Prefab UI builder rendering the find/view/decide/mutate card shape consistent with update_order_status
- Markdown templates (preview + result) for non-Prefab clients

Bug fix included: all four result schemas (StatusChangeResult plus the three new ones) had `confirmed: Literal[True]` that contradicted their use on the user-declined path. Now `confirmed: bool` with declined-path constructors passing False explicitly. Test added pinning the contract.

Closes #39.

Author: dougborg

statuspro_mcp_server/src/statuspro_mcp/templates/bulk_status_change_preview.md

@@ -0,0 +1,11 @@
+# Preview: bulk status change ({order_count} orders)
+
+**Target status:** {target_status_name} ({target_status_code})
+
+**Order IDs:** {ids_preview}
+
+{comment_block}
+
+Emails: {recipients}
+
+Rerun with `confirm=true` to bulk-update all {order_count} orders.

statuspro_mcp_server/src/statuspro_mcp/templates/bulk_status_change_result.md

@@ -0,0 +1,5 @@
+# Bulk status change ({order_count} orders)
+
+- **Target status:** {target_status_code}
+- **Result:** {outcome}
+- **HTTP:** {http_status}{note_line}{message_line}

statuspro_mcp_server/src/statuspro_mcp/templates/comment_preview.md

@@ -0,0 +1,7 @@
+# Preview: comment on order {order_id}
+
+**Order:** {order_label}
+
+**Comment** ({visibility}): {comment}
+
+Rerun with `confirm=true` to add the comment.

statuspro_mcp_server/src/statuspro_mcp/templates/comment_result.md

@@ -0,0 +1,4 @@
+# Comment on order {order_id}
+
+- **Result:** {outcome}
+- **HTTP:** {http_status}{message_line}

statuspro_mcp_server/src/statuspro_mcp/templates/due_date_change_preview.md

@@ -0,0 +1,8 @@
+# Preview: due date for order {order_id}
+
+**Order:** {order_label}
+
+**Current:** {current_due_date}{current_range}
+**Proposed:** {new_due_date}{new_range}
+
+Rerun with `confirm=true` to apply the due date change.

statuspro_mcp_server/src/statuspro_mcp/templates/due_date_change_result.md

@@ -0,0 +1,5 @@
+# Due date change for order {order_id}
+
+- **New due date:** {new_due_date}{new_range}
+- **Result:** {outcome}
+- **HTTP:** {http_status}{message_line}