fix(tui): prevent terminal cell artifacts

tui/src/app.test.ts

@@ -646,13 +646,28 @@ describe("NanobotTui layout", () => {
       runtimeControls: {
         modelText: TextRenderable
         accessText: TextRenderable
+        contextText: TextRenderable
         visible: boolean
         menuRoot: { getChildren(): unknown[] }
       }
+      titleText: TextRenderable
+      status: TextRenderable
+      meta: TextRenderable
     }
 
     try {
       await waitUntil(() => (app as unknown as { ready: boolean }).ready)
+      await setup.renderOnce()
+      expect(setup.renderer.getCursorState()).toMatchObject({
+        style: "line",
+        blinking: false,
+      })
+      expect(ui.runtimeControls.modelText.selectable).toBe(false)
+      expect(ui.runtimeControls.accessText.selectable).toBe(false)
+      expect(ui.runtimeControls.contextText.selectable).toBe(false)
+      expect(ui.titleText.selectable).toBe(false)
+      expect(ui.status.selectable).toBe(false)
+      expect(ui.meta.selectable).toBe(false)
       app.accept({ event: "goal_status", chat_id: "chat", status: "running" })
       await setup.flush()
       await setup.mockMouse.click(
@@ -662,6 +677,7 @@ describe("NanobotTui layout", () => {
       await waitUntil(() => ui.runtimeControls.visible)
       await setup.flush()
       const modelRows = ui.runtimeControls.menuRoot.getChildren() as TextRenderable[]
+      expect(modelRows.every((row) => !row.selectable)).toBe(true)
       const fast = modelRows.find((row) => row.plainText.includes("fast"))
       if (!fast) throw new Error("fast model row was not rendered")
       await setup.mockMouse.click(fast.x + 2, fast.y)
@@ -1431,6 +1447,24 @@ describe("NanobotTui layout", () => {
     expect(setup.renderer.getSelection()).toBeNull()
   })
 
+  test("clears transcript selection when clicking non-content chrome", async () => {
+    setup = await createRenderer({ width: 72, height: 20, screenMode: "alternate-screen" })
+    const app = mount(setup)
+    const status = (app as unknown as { status: TextRenderable }).status
+    app.accept({ event: "delta", chat_id: "chat", text: "selectable answer" })
+    app.accept({ event: "stream_end", chat_id: "chat" })
+    await setup.flush()
+
+    const rows = setup.captureCharFrame().split("\n")
+    const y = rows.findIndex((row) => row.includes("selectable answer"))
+    const x = rows[y]?.indexOf("selectable answer") ?? -1
+    await setup.mockMouse.drag(x, y, x + "selectable answer".length, y)
+    expect(setup.renderer.getSelection()?.getSelectedText()).toBe("selectable answer")
+
+    await setup.mockMouse.click(status.x, status.y)
+    expect(setup.renderer.getSelection()).toBeNull()
+  })
+
   test("animates one stable status line while the agent works", async () => {
     setup = await createRenderer({ width: 88, height: 24, screenMode: "alternate-screen" })
     const app = mount(setup)

tui/src/app.ts

@@ -479,6 +479,14 @@ export class NanobotTui {
       paddingRight: 1,
       flexDirection: "column",
       backgroundColor: RGBA.defaultBackground(),
+      onMouseDown: (event) => {
+        // Selection belongs to transcript/input content, never to empty chrome.
+        // Clearing it here prevents default-background cells from lingering as
+        // opaque blocks in terminals with differential repainting.
+        if (event.button === 0 && event.target && !event.target.selectable) {
+          this.renderer.clearSelection()
+        }
+      },
     })
     this.title = new BoxRenderable(renderer, {
       id: "nanobot-tui-title",
@@ -496,6 +504,7 @@ export class NanobotTui {
       flexShrink: 0,
       truncate: true,
       fg: this.palette.muted,
+      selectable: false,
     })
     this.runtimeControls = new RuntimeControls(
       renderer,
@@ -553,6 +562,9 @@ export class NanobotTui {
       backgroundColor: composerSurface,
       focusedBackgroundColor: composerSurface,
       cursorColor: this.palette.accent,
+      // A steady line cursor avoids the block-cell trails produced by some
+      // terminals when a retained full-screen UI redraws around the composer.
+      cursorStyle: { style: "line", blinking: false },
       showCursor: true,
       keyBindings: [
         { name: "return", shift: true, action: "newline" },
@@ -586,6 +598,7 @@ export class NanobotTui {
       minWidth: 0,
       flexGrow: 1,
       flexShrink: 1,
+      selectable: false,
     })
     this.meta = new TextRenderable(renderer, {
       id: "nanobot-tui-meta",
@@ -594,6 +607,7 @@ export class NanobotTui {
       height: 1,
       width: "auto",
       flexShrink: 1,
+      selectable: false,
     })
 
     const statusRow = new BoxRenderable(renderer, {

tui/src/picker-menu.ts

@@ -119,6 +119,7 @@ export class PickerMenu<T> {
         width: "100%",
         height: 1,
         fg: this.theme.muted,
+        selectable: false,
       }))
       return
     }
@@ -131,6 +132,7 @@ export class PickerMenu<T> {
         height: 1,
         wrapMode: "none",
         fg: selected ? this.theme.text : this.theme.muted,
+        selectable: false,
         ...(selected && this.theme.selectedBackground
           ? { backgroundColor: RGBA.fromHex(this.theme.selectedBackground) }
           : {}),

tui/src/runtime-controls.ts

@@ -81,6 +81,7 @@ export class RuntimeControls {
       height: 1,
       flexShrink: 0,
       fg: theme.faint,
+      selectable: false,
     })
     this.render()
   }
@@ -159,6 +160,7 @@ export class RuntimeControls {
       height: 1,
       flexShrink: id === "model" ? 1 : 0,
       fg: this.theme.muted,
+      selectable: false,
       onMouseOver: () => { text.fg = this.theme.accent },
       onMouseOut: () => this.renderColors(),
       onMouseDown: (event) => {