fix(help): don't trim example result beginning (#16353)

# Description
The `help` command, when printing the examples with results, trims the
first line and it appears unindented compared to the following lines.

- Before:
<img width="1110" height="346" alt="image"
src="https://github.com/user-attachments/assets/3487381d-3631-49c9-bb0e-f7ad958b7291"
/>

- After:
<img width="1123" height="339" alt="image"
src="https://github.com/user-attachments/assets/acb45afd-0492-49d2-a5cb-5130bbb4cf94"
/>

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crates/nu-engine/src/documentation.rs

@@ -497,8 +497,9 @@ fn get_command_documentation(
                     long_desc,
                     "  {}",
                     item.to_expanded_string("", nu_config)
+                        .trim_end()
+                        .trim_start_matches(|c: char| c.is_whitespace() && c != ' ')
                         .replace('\n', "\n  ")
-                        .trim()
                 );
             }
         }