fix(#271): document name?, body_name? and targets? on the commands that accept them

sheet.flange now lists name?/body_name?, solid.loft and solid.sweep list
targets?/name?/body_name?, and the primitives list name?/body_name? (all go
through add_feature, which reads them). A test pins the shared keys for
every body-creating feature.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RjGw4gA5ZvKrU8MQP6sBgT

crates/engine/src/cmd/sheet.rs

@@ -16,7 +16,7 @@ pub static COMMANDS: &[CommandSpec] = &[
     CommandSpec::new("sheet.flange", "Flange", flange).at("SHEET METAL", "CREATE").icon("flange").params(
         "base: sketch + profiles? (rule?, flip?) | contour: sketch + curves (open chain of lines) + distance (rule?, flip?, reverse?) | \
          edge: edges: [[x,y,z] on top/bottom edges] + height (to the outer face), angle? (default 90 deg), radius? (default: rule), \
-         position?: inside|outside|middle, flip?, body?; type?: base|edge|contour (default from the inputs)",
+         position?: inside|outside|middle, flip?, body?; type?: base|edge|contour (default from the inputs); name?, body_name? (the new body)",
     ),
     CommandSpec::new("sheet.hem", "Hem", hem)
         .at("SHEET METAL", "CREATE")