Normalize whitespace-only lines in agent messages (#34772)

## What changed

Apply the existing whitespace-only line normalization to both streaming and
finalized agent Markdown. Blank lines now discard indentation and stale
hyperlinks while preserving their line style.

GitOrigin-RevId: f6150190b02f8cd8c853220cae1a2dcd2f4578a5

codex-rs/tui/src/app/snapshots/codex_tui__app__tests__required_stream_reflow_during_capped_initial_replay.snap

@@ -5,7 +5,7 @@ expression: "rendered.lines.iter().map(rendered_line_text).collect::<Vec<_>>().j
 latest user question
 
 • Final answer:
-  
+
    Pattern       Outcome
   ━━━━━━━━━━━━  ━━━━━━━━━━━
    Table tail    Preserved

codex-rs/tui/src/app/snapshots/codex_tui__app__tests__required_stream_reflow_during_capped_initial_replay_survives_transcript_overlay.snap

@@ -5,7 +5,7 @@ expression: "rendered.lines.iter().map(rendered_line_text).collect::<Vec<_>>().j
 latest user question
 
 • Final answer:
-  
+
    Pattern       Outcome
   ━━━━━━━━━━━━  ━━━━━━━━━━━
    Table tail    Preserved

codex-rs/tui/src/history_cell/messages.rs

@@ -407,6 +407,21 @@ impl AgentMarkdownCell {
     }
 }
 
+fn normalize_whitespace_only_hyperlink_lines(mut lines: Vec<HyperlinkLine>) -> Vec<HyperlinkLine> {
+    for line in &mut lines {
+        if line
+            .line
+            .spans
+            .iter()
+            .all(|span| span.content.chars().all(char::is_whitespace))
+        {
+            line.line = Line::default().style(line.line.style);
+            line.hyperlinks.clear();
+        }
+    }
+    lines
+}
+
 impl HistoryCell for AgentMarkdownCell {
     fn display_lines(&self, width: u16) -> Vec<Line<'static>> {
         visible_lines(self.display_hyperlink_lines(width))
@@ -432,7 +447,11 @@ impl HistoryCell for AgentMarkdownCell {
                 Some(self.cwd.as_path()),
                 self.inline_visualization_context.as_ref(),
             );
-            prefix_hyperlink_lines(lines, "• ".dim(), "  ".into())
+            normalize_whitespace_only_hyperlink_lines(prefix_hyperlink_lines(
+                lines,
+                "• ".dim(),
+                "  ".into(),
+            ))
         };
 
         if let Some(rendered_lines) = &self.rendered_lines {
@@ -487,7 +506,7 @@ impl HistoryCell for StreamingAgentTailCell {
     fn display_hyperlink_lines(&self, _width: u16) -> Vec<HyperlinkLine> {
         // Tail lines are already rendered at the controller's current stream width.
         // Re-wrapping them here can split table borders and produce malformed in-flight rows.
-        let mut lines = prefix_hyperlink_lines(
+        normalize_whitespace_only_hyperlink_lines(prefix_hyperlink_lines(
             self.lines.clone(),
             if self.is_first_line {
                 "• ".dim()
@@ -495,19 +514,7 @@ impl HistoryCell for StreamingAgentTailCell {
                 "  ".into()
             },
             "  ".into(),
-        );
-        for line in &mut lines {
-            if line
-                .line
-                .spans
-                .iter()
-                .all(|span| span.content.chars().all(char::is_whitespace))
-            {
-                line.line = Line::default().style(line.line.style);
-                line.hyperlinks.clear();
-            }
-        }
-        lines
+        ))
     }
 
     fn transcript_hyperlink_lines(&self, width: u16) -> Vec<HyperlinkLine> {

codex-rs/tui/src/history_cell/snapshots/codex_tui__history_cell__tests__raw_mode_toggle_transcript.snap

@@ -9,11 +9,11 @@ rich before:
 
 • - first item
   - second item
-  
+
    Col     Value
   ━━━━━━  ━━━━━━━
    code    x = 1
-  
+
   copy me
 • Called
   └ workspace.inspect({"path":"README.md
@@ -45,11 +45,11 @@ rich after:
 
 • - first item
   - second item
-  
+
    Col     Value
   ━━━━━━  ━━━━━━━
    code    x = 1
-  
+
   copy me
 • Called
   └ workspace.inspect({"path":"README.md

codex-rs/tui/src/snapshots/codex_tui__inline_visualization__tests__agent_code_blocks_preserve_visualization_directive_literals.snap

@@ -3,9 +3,9 @@ source: tui/src/inline_visualization_tests.rs
 expression: text
 ---
 • Fenced:
-  
+
   ::codex-inline-vis{file="chart.html"}
-  
+
   Indented:
-  
+
       ::codex-inline-vis{file="chart.html"}

codex-rs/tui/src/snapshots/codex_tui__inline_visualization__tests__finalized_agent_cell_visualization_link.snap

@@ -3,8 +3,8 @@ source: tui/src/inline_visualization_tests.rs
 expression: snapshot_text
 ---
 • Before
-  
+
   Open chart visualization in the browser
   file://<viewer-path>
-  
+
   After