W21 Phase 1: locked selectable display fields for node ID + ticket

Add a read-only-but-selectable "locked" mode to the A9 ContextInput so
share-critical values (full node ID, full room ticket) can be drag-selected
and copied with the mouse/keyboard, in addition to the existing one-click
Copy buttons (which are kept).

- context_input.rs: add `locked` flag + builder + `locked_value(value, noop)`
  constructor. A controlled text_input with a no-op on_input stays focusable
  and selection-capable while never mutating (iced treats on_input==None as
  Disabled, verified against iced_widget-0.14.2 source).
- Extract overlay gating into a pure `menu_action_enabled` seam: when locked,
  Cut/Paste are disabled, Copy is enabled with a (non-secure) selection, and
  Select All is enabled when there's a value. +1 unit test.
- app/mod.rs: add AppMessage::Noop; render the full node ID and full ticket in
  width-capped locked fields beside their existing Copy buttons.

Phase 2 (cross-message selectable chat transcript) intentionally deferred:
it requires a transcript-level custom widget that owns selection/layout/hit-
testing while preserving A13 links and attachment rows — out of scope for a
bounded edit. Design path recorded in the Codex task report.

Tests-green only (460 lib, clippy clean, release build green); wants a quick
field check of mouse drag-select + right-click Copy + Ctrl+A/C.

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

src/widget/context_input.rs

@@ -105,6 +105,20 @@ where
     ContextInput::new(placeholder, value)
 }
 
+pub fn locked_value<'a, Message, Theme, Renderer>(
+    value: &str,
+    noop: Message,
+) -> ContextInput<'a, Message, Theme, Renderer>
+where
+    Message: Clone + 'a,
+    Theme: text_input::Catalog + 'a,
+    Renderer: text::Renderer,
+{
+    ContextInput::new("", value)
+        .on_input(move |_| noop.clone())
+        .locked(true)
+}
+
 pub struct ContextInput<
     'a,
     Message,
@@ -117,6 +131,7 @@ pub struct ContextInput<
     input: text_input::TextInput<'a, Message, Theme, Renderer>,
     value: String,
     is_secure: bool,
+    locked: bool,
     on_input: Option<Rc<dyn Fn(String) -> Message + 'a>>,
     on_paste: Option<Rc<dyn Fn(String) -> Message + 'a>>,
     style: Option<InputStyleFn<'a, Theme>>,
@@ -134,6 +149,7 @@ where
             input: text_input::TextInput::new(placeholder, value),
             value: value.to_owned(),
             is_secure: false,
+            locked: false,
             on_input: None,
             on_paste: None,
             style: None,
@@ -151,6 +167,11 @@ where
         self
     }
 
+    pub fn locked(mut self, yes: bool) -> Self {
+        self.locked = yes;
+        self
+    }
+
     pub fn on_input(
         mut self,
         on_input: impl Fn(String) -> Message + 'a,
@@ -448,6 +469,7 @@ where
             input_state,
             value: &self.value,
             is_secure: self.is_secure,
+            locked: self.locked,
             on_input: self.on_input.clone(),
             on_paste: self.on_paste.clone(),
             style: self.style.clone(),
@@ -479,6 +501,7 @@ where
     input_state: &'a mut text_input::State<Renderer::Paragraph>,
     value: &'a str,
     is_secure: bool,
+    locked: bool,
     on_input: Option<Rc<dyn Fn(String) -> Message + 'a>>,
     on_paste: Option<Rc<dyn Fn(String) -> Message + 'a>>,
     style: Option<InputStyleFn<'a, Theme>>,
@@ -686,13 +709,13 @@ where
         let has_selection = menu.selection.0 != menu.selection.1;
         let has_value = !text_input::Value::new(self.value).is_empty();
 
-        match action {
-            MenuAction::Cut | MenuAction::Copy => {
-                has_selection && !self.is_secure
-            }
-            MenuAction::Paste => true,
-            MenuAction::SelectAll => has_value,
-        }
+        menu_action_enabled(
+            action,
+            has_selection,
+            has_value,
+            self.is_secure,
+            self.locked,
+        )
     }
 
     fn hit_action(
@@ -811,6 +834,21 @@ fn disabled_color(color: Color) -> Color {
     }
 }
 
+fn menu_action_enabled(
+    action: MenuAction,
+    has_selection: bool,
+    has_value: bool,
+    is_secure: bool,
+    locked: bool,
+) -> bool {
+    match action {
+        MenuAction::Cut => has_selection && !is_secure && !locked,
+        MenuAction::Copy => has_selection && !is_secure,
+        MenuAction::Paste => !locked,
+        MenuAction::SelectAll => has_value,
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -891,4 +929,15 @@ mod tests {
             }
         );
     }
+
+    #[test]
+    fn locked_menu_allows_copy_and_select_all_only() {
+        assert!(!menu_action_enabled(MenuAction::Cut, true, true, false, true));
+        assert!(menu_action_enabled(MenuAction::Copy, true, true, false, true));
+        assert!(!menu_action_enabled(MenuAction::Paste, true, true, false, true));
+        assert!(menu_action_enabled(MenuAction::SelectAll, true, true, false, true));
+
+        assert!(!menu_action_enabled(MenuAction::Copy, false, true, false, true));
+        assert!(!menu_action_enabled(MenuAction::SelectAll, false, false, false, true));
+    }
 }