Storm Sewer: fix prompt flow — collect typed values before the click

The structure/pipe commands took a viewport interaction first and then asked
for typed values. But a point-pick result (NeedPoint) does not re-focus the
command line, so after the click the typed digits went nowhere and Enter hit
on_enter -> Cancel ("Command cancelled.").

Reorder both commands to the OFFSET-style flow: collect typed values first
(command line focused at dispatch and kept focused through text input), then
take the viewport click last and commit from it.

- PlaceStructure: enter invert/rim/area/C, then click the location.
- PlacePipe: enter diameter/n, then click START and END structures; commit
  from the second pick using the click points (connectivity stays exact via
  structure handles).
- Dispatch arms focus the command line so the first prompt is typeable.
- Reverts the update.rs inject_picked_entity allow-list change (the pt-based
  pipe no longer needs the picked entity).

15 module tests updated and green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/app/commands.rs

@@ -68,11 +68,14 @@ impl OpenCADStudio {
                 };
                 self.command_line.push_info(&cmd.prompt());
                 self.tabs[i].active_cmd = Some(Box::new(cmd));
+                // Focus the command line so the first typed value is captured.
+                return self.focus_cmd_input();
             }
             "SS_PIPE" => {
                 let cmd = crate::modules::storm_sewer::structures::PlacePipe::new();
                 self.command_line.push_info(&cmd.prompt());
                 self.tabs[i].active_cmd = Some(Box::new(cmd));
+                return self.focus_cmd_input();
             }
             "SS_PROFILE" => {
                 use crate::modules::storm_sewer::analysis as ss;

src/app/update.rs

@@ -2812,7 +2812,7 @@ impl OpenCADStudio {
                                     .map(|c| {
                                         matches!(
                                             c.name(),
-                                            "DIMTEDIT" | "MLEADERADD" | "MLEADERREMOVE" | "SS_PIPE"
+                                            "DIMTEDIT" | "MLEADERADD" | "MLEADERREMOVE"
                                         )
                                     })
                                     .unwrap_or(false);