merge: TEXTEDIT command + TEXTEDITMODE sysvar (#130)

Merge PR #130 (KarimJerbi) and resolve review findings:

- Conflict (settings.rs): keep current persisted-settings layout, append
  texteditmode field.
- Conflict (command/mod.rs): keep both new CmdResult variants — main's
  live-entity ops and the PR's text-edit suspend/resume.
- Bug: invalid TEXTEDITMODE value no longer aborts via the Measurement
  arm; it now re-prompts with the error and stays active.
- Dedup: single parse_texteditmode() helper replaces the value parsing
  duplicated across commands.rs, settings.rs and textedit.rs.
- Strip trailing whitespace.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/command/mod.rs

@@ -240,6 +240,12 @@ pub enum CmdResult {
         entity: EntityType,
         finish: bool,
     },
+    /// Suspends command execution, moves it to suspended_cmd, and opens the text editor for the given handle.
+    SuspendForTextEdit { handle: Handle },
+    /// Requests a standard document-level undo while keeping the command active.
+    UndoDocument,
+    /// Sets the TEXTEDITMODE system variable and ends the command.
+    SetTexteditMode(bool),
 }
 
 /// What kind of value the active command is currently asking for. Drives
@@ -427,6 +433,11 @@ pub trait CadCommand: Send {
         false
     }
 
+    /// Called when the text editor closes, either because the user committed or cancelled the edit.
+    fn on_editor_closed(&mut self, _committed: bool) -> CmdResult {
+        CmdResult::Cancel
+    }
+
     /// Called when the user clicks and `needs_entity_pick()` is true.
     /// `handle` is the nearest wire's entity handle (Handle::NULL if nothing found).
     fn on_entity_pick(&mut self, _handle: Handle, _pt: Vec3) -> CmdResult {