feat(commands): interactive value prompts for PDMODE/PDSIZE/LTSCALE/CELTSCALE (F4)

Bare PDMODE / PDSIZE / LTSCALE / CELTSCALE now enter a generic
ValuePromptCommand front-end that prompts for the value and delegates to the
existing inline `<name> <value>` handler via CmdResult::Dispatch, so they
prompt step-by-step like UCS. A bare Enter reports the current value;
`PDMODE 3` still works as one typed / headless line.

Only pure single-value setting commands are converted. Dialog-opening
commands (LAYER, PURGE, DIMSTYLE, STYLE …) intentionally keep their
bare-name behaviour (open the panel), and subcommand-tree commands keep
their inline handlers — all already typable with arguments since F1.

Adds headless test value_prompt_commands_inline_args. Fourth phase of the
unified step driver.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/automation.rs

@@ -497,6 +497,27 @@ mod tests {
         );
     }
 
+    #[test]
+    fn value_prompt_commands_inline_args() {
+        // A single-value setting command entered with its value on one line
+        // drives the interactive front-end (start + value step) and applies via
+        // the inline handler. (F4)
+        let mut app = OpenCADStudio::new_for_test();
+        app.automation_op(r#"{"op":"new"}"#);
+        app.automation_op(r#"{"op":"run","cmd":"PDMODE 3"}"#);
+        app.automation_op(r#"{"op":"run","cmd":"LTSCALE 2.5"}"#);
+        let i = app.active_tab;
+        let h = &app.tabs[i].scene.document.header;
+        assert_eq!(h.point_display_mode, 3, "PDMODE 3 should set point mode");
+        assert!(
+            (h.linetype_scale - 2.5).abs() < 1e-9,
+            "LTSCALE 2.5 should set scale, got {}",
+            h.linetype_scale
+        );
+        // No command should be left dangling.
+        assert!(app.tabs[i].active_cmd.is_none(), "command must have finished");
+    }
+
     #[test]
     fn save_then_open_round_trips() {
         let mut app = OpenCADStudio::new_for_test();

src/app/commands.rs

@@ -4944,7 +4944,13 @@ impl OpenCADStudio {
                     }
                 }
             }
-            cmd if cmd == "LTSCALE" || cmd.starts_with("LTSCALE ") => {
+            "LTSCALE" => {
+                use crate::command::ValuePromptCommand;
+                let c = ValuePromptCommand::new("LTSCALE", "LTSCALE  new global line-type scale:");
+                self.command_line.push_info(&c.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(c));
+            }
+            cmd if cmd.starts_with("LTSCALE ") => {
                 let val_str = cmd.trim_start_matches("LTSCALE").trim();
                 if val_str.is_empty() {
                     let v = self.tabs[i].scene.document.header.linetype_scale;
@@ -4964,7 +4970,16 @@ impl OpenCADStudio {
                     self.command_line.push_error("Usage: LTSCALE [value]");
                 }
             }
-            cmd if cmd == "PDMODE" || cmd.starts_with("PDMODE ") => {
+            "PDMODE" => {
+                use crate::command::ValuePromptCommand;
+                let c = ValuePromptCommand::new(
+                    "PDMODE",
+                    "PDMODE  new value [0=dot 1=none 2=+ 3=x 4=tick; +32 circle +64 square]:",
+                );
+                self.command_line.push_info(&c.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(c));
+            }
+            cmd if cmd.starts_with("PDMODE ") => {
                 let val_str = cmd.trim_start_matches("PDMODE").trim();
                 if val_str.is_empty() {
                     let v = self.tabs[i].scene.document.header.point_display_mode;
@@ -4999,7 +5014,16 @@ impl OpenCADStudio {
                         .push_error("Requires 0 OR 1 OR MULTIPLE OR SINGLE");
                 }
             }
-            cmd if cmd == "PDSIZE" || cmd.starts_with("PDSIZE ") => {
+            "PDSIZE" => {
+                use crate::command::ValuePromptCommand;
+                let c = ValuePromptCommand::new(
+                    "PDSIZE",
+                    "PDSIZE  new point size (0 = 5% of viewport, <0 = absolute):",
+                );
+                self.command_line.push_info(&c.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(c));
+            }
+            cmd if cmd.starts_with("PDSIZE ") => {
                 let val_str = cmd.trim_start_matches("PDSIZE").trim();
                 if val_str.is_empty() {
                     let v = self.tabs[i].scene.document.header.point_display_size;
@@ -5057,7 +5081,16 @@ impl OpenCADStudio {
                     }
                 }
             }
-            cmd if cmd == "CELTSCALE" || cmd.starts_with("CELTSCALE ") => {
+            "CELTSCALE" => {
+                use crate::command::ValuePromptCommand;
+                let c = ValuePromptCommand::new(
+                    "CELTSCALE",
+                    "CELTSCALE  new current-object line-type scale:",
+                );
+                self.command_line.push_info(&c.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(c));
+            }
+            cmd if cmd.starts_with("CELTSCALE ") => {
                 let val_str = cmd.trim_start_matches("CELTSCALE").trim();
                 if val_str.is_empty() {
                     let v = self.tabs[i]

src/command/mod.rs

@@ -79,6 +79,57 @@ pub enum StepInput {
     Escape,
 }
 
+/// Generic interactive front-end for a single-value setting command (PDMODE,
+/// PDSIZE, LTSCALE, CELTSCALE, …). Bare `<name>` enters this command, which
+/// prompts for one value and then delegates to the existing inline
+/// `<name> <value>` handler via [`CmdResult::Dispatch`]. A bare Enter delegates
+/// to `<name> ` (trailing space) so the inline handler reports the current
+/// value. Keeps the value math + persistence in the one inline place while
+/// making the command prompt for its argument step-by-step.
+pub struct ValuePromptCommand {
+    name: &'static str,
+    prompt: &'static str,
+}
+
+impl ValuePromptCommand {
+    pub fn new(name: &'static str, prompt: &'static str) -> Self {
+        Self { name, prompt }
+    }
+}
+
+impl CadCommand for ValuePromptCommand {
+    fn name(&self) -> &'static str {
+        self.name
+    }
+
+    fn prompt(&self) -> String {
+        self.prompt.to_string()
+    }
+
+    fn wants_text_input(&self) -> bool {
+        true
+    }
+
+    fn on_text_input(&mut self, text: &str) -> Option<CmdResult> {
+        let t = text.trim();
+        if t.is_empty() {
+            Some(CmdResult::Dispatch(format!("{} ", self.name)))
+        } else {
+            Some(CmdResult::Dispatch(format!("{} {t}", self.name)))
+        }
+    }
+
+    fn on_point(&mut self, _pt: DVec3) -> CmdResult {
+        // A value command takes no point; ignore stray clicks, keep prompting.
+        CmdResult::NeedPoint
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        // Bare Enter → report the current value via the inline handler.
+        CmdResult::Dispatch(format!("{} ", self.name))
+    }
+}
+
 // ── Result token ──────────────────────────────────────────────────────────
 
 /// Returned by every `CadCommand` method to tell main.rs what to do.