gui: add a placeholder notes search bar to the header

Adds NotesSearchBar as its own component (rust/gui-app/src/agents/notes/search_bar.rs)
so a richer search interface can grow there later. Moves the note title/timestamps
out of the shared header into a compact bordered row atop the content column,
freeing the header for the "Notes" label plus the search bar, which is left-aligned
with the content column and capped at 500px wide.

rust/gui-app/src/agents/notes/mod.rs

@@ -9,6 +9,7 @@
 //! executor and folds back into the view via `Entity::update`.
 
 pub mod editor;
+pub mod search_bar;
 
 use std::collections::HashMap;
 use std::sync::Arc;
@@ -25,6 +26,7 @@ use synchronicity::node::NodePubkey;
 use synchronicity::stores::Store;
 
 use self::editor::{NoteEditor, NoteEditorEvent};
+use self::search_bar::NotesSearchBar;
 use crate::agent_sidebar::{AgentSidebar, View};
 use crate::components::button::button;
 use crate::components::hierarchical_sidebar::{
@@ -143,6 +145,8 @@ pub struct NotesView {
     _context_menu_sub: Option<Subscription>,
     dialog: Option<Dialog>,
     error: Option<SharedString>,
+    /// Placeholder search bar shown at the right edge of the header.
+    search_bar: Entity<NotesSearchBar>,
 }
 
 impl NotesView {
@@ -179,6 +183,8 @@ impl NotesView {
         })
         .detach();
 
+        let search_bar = cx.new(NotesSearchBar::new);
+
         let mut this = Self {
             store,
             node,
@@ -201,6 +207,7 @@ impl NotesView {
             _context_menu_sub: None,
             dialog: None,
             error: None,
+            search_bar,
         };
         this.reload_notebooks(None, cx);
         this
@@ -662,12 +669,22 @@ impl Render for NotesView {
         self.ensure_context_menu(window, cx);
 
         let dragging = self.sidebar_resize.is_dragging();
+        let content_column = div()
+            .flex()
+            .flex_col()
+            .flex_1()
+            .min_w(px(0.))
+            .min_h(px(0.))
+            .when_some(self.note_meta.as_ref(), |c, meta| {
+                c.child(self.render_note_meta_row(&theme, meta, tz))
+            })
+            .child(self.render_content(&theme));
         let root = div()
             .relative()
             .flex()
             .flex_col()
             .size_full()
-            .child(self.render_header(&theme, tz))
+            .child(self.render_header(&theme))
             .child(
                 div()
                     .flex()
@@ -682,7 +699,7 @@ impl Render for NotesView {
                         cx,
                         |this| &mut this.sidebar_resize,
                     ))
-                    .child(self.render_content(&theme)),
+                    .child(content_column),
             )
             .when_some(self.render_context_menu(), |c, menu| c.child(menu))
             .when(self.dialog.is_some(), |c| c.child(self.render_dialog(&theme, cx)))
@@ -692,7 +709,12 @@ impl Render for NotesView {
 }
 
 impl NotesView {
-    fn render_header(&self, theme: &Theme, tz: Option<chrono_tz::Tz>) -> impl IntoElement + use<> {
+    /// The top bar: the "Notes" label over the sidebar column, and the search
+    /// bar starting at the content column's left edge (same as the note meta
+    /// row below it). The note meta (title + timestamps) used to live here but
+    /// now sits in its own compact row atop the content column, so it stays
+    /// clear of the sidebar.
+    fn render_header(&self, theme: &Theme) -> impl IntoElement + use<> {
         div()
             .flex()
             .flex_row()
@@ -703,7 +725,7 @@ impl NotesView {
             .border_color(theme.border_default)
             .child(
                 // The "Notes" label sits over the sidebar column; its width plus the
-                // resize divider lines up the note meta with the content pane's edge.
+                // resize divider lines up the content column below with its edge.
                 div()
                     .w(self.sidebar_resize.width() + px(resizable::DIVIDER_WIDTH))
                     .flex_none()
@@ -713,16 +735,16 @@ impl NotesView {
                     .text_color(theme.text_primary)
                     .child("Notes"),
             )
-            .when_some(self.note_meta.as_ref(), |c, meta| {
-                c.child(self.render_note_meta(theme, meta, tz))
-            })
+            .child(div().flex_1().min_w(px(0.)).flex().px_4().child(self.search_bar.clone()))
     }
 
-    /// The active note's title with its created and last-modified timestamps
-    /// beneath, shown in the header bar starting at the content pane's left edge.
+    /// A compact row atop the content column showing the open note's title and
+    /// its created/modified timestamps on a single line, bordered below to
+    /// separate it from the note body. Bounded on the left by the sidebar since
+    /// it lives inside the content column, not the shared header.
     /// The title is read live from [`Self::items`] (the tree's single source of
     /// truth) so an inline rename is reflected without re-selecting the note.
-    fn render_note_meta(
+    fn render_note_meta_row(
         &self,
         theme: &Theme,
         meta: &NoteMeta,
@@ -735,15 +757,18 @@ impl NotesView {
             .map(|info| info.title.clone())
             .unwrap_or_else(|| DEFAULT_ITEM_NAME.into());
         div()
+            .flex_none()
             .flex()
-            .flex_col()
-            .justify_center()
-            .gap_1()
-            .flex_1()
-            .min_w_0()
+            .flex_row()
+            .items_center()
+            .gap_3()
+            .h(px(36.))
             .px_4()
+            .border_b_1()
+            .border_color(theme.border_default)
             .child(
                 div()
+                    .flex_none()
                     .text_base()
                     .font_weight(FontWeight::BOLD)
                     .text_color(theme.text_primary)
@@ -755,7 +780,8 @@ impl NotesView {
                 div()
                     .flex()
                     .flex_row()
-                    .gap_4()
+                    .flex_none()
+                    .gap_3()
                     .text_size(px(12.))
                     .text_color(theme.text_secondary)
                     .child(div().child(SharedString::from(format!(

rust/gui-app/src/agents/notes/search_bar.rs

@@ -0,0 +1,40 @@
+//! The notes search bar shown at the right edge of the header.
+//!
+//! Currently just a text field with no wired-up behavior — a placeholder for
+//! what should grow into a richer search interface (scoping to a notebook,
+//! filters, live results, etc.). It's kept as its own component from the start
+//! so that growth happens here rather than in [`super::NotesView`].
+
+use gpui::{Context, Entity, IntoElement, Render, Window, div, prelude::*, px};
+
+use crate::components::text_input::TextInput;
+
+/// A search field this wide gives room for a richer query (filters, scoped
+/// terms) while staying well under the ~600px line length past which a
+/// single-line field gets hard to scan; it also keeps the bar from
+/// stretching across ultrawide monitors.
+const MAX_WIDTH: f32 = 500.;
+
+pub struct NotesSearchBar {
+    input: Entity<TextInput>,
+}
+
+impl NotesSearchBar {
+    pub fn new(cx: &mut Context<Self>) -> Self {
+        let input = cx.new(|cx| TextInput::new(cx, "Search notes…"));
+        Self { input }
+    }
+}
+
+impl Render for NotesSearchBar {
+    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+        div()
+            .flex()
+            .flex_row()
+            .items_center()
+            .w_full()
+            .max_w(px(MAX_WIDTH))
+            .min_w(px(0.))
+            .child(self.input.clone())
+    }
+}