chore(format): strip trailing blank lines at EOF (codex diff-check fix)

The previous split commit (764eb9f4) left three files with an
extra blank line after the closing `}` because the sed/awk
extraction pipeline appended one. `git diff --check` flagged:

  crates/openpencil-shell-core/src/mcp/parser.rs:344
  crates/openpencil-shell-core/src/mcp/tools.rs:278
  crates/openpencil-shell-core/src/widgets/property_panel.rs:585

All three normalized to end with exactly one newline after the
final `}`. No semantic change.

crates/openpencil-shell-core/src/mcp/parser.rs

@@ -341,4 +341,3 @@ fn extract_field<'a>(line: &'a str, key: &str) -> Option<&'a str> {
         .unwrap_or(val.len());
     Some(line[val_start..val_start + end_rel].trim())
 }
-

crates/openpencil-shell-core/src/mcp/tools.rs

@@ -275,4 +275,3 @@ fn walk_node(
         walk_node(child, node.id.raw(), out);
     }
 }
-

crates/openpencil-shell-core/src/widgets/property_panel.rs

@@ -582,4 +582,3 @@ impl Widget for PropertyPanel {
         node
     }
 }
-