feat(tui): integrate table rendering into streaming pipeline with reflow

Wire the Unicode box-drawing table renderer into the live streaming
path with holdback-aware commit logic, post-stream cell consolidation,
and debounced resize reflow.

Key additions:
- StreamCore: shared bookkeeping deduplicating Stream/PlanStreamController
- Table holdback: fence-aware state machine keeps buffer mutable during table detection
- AgentMarkdownCell: stores raw markdown source, re-renders at any width on demand
- ConsolidateAgentMessage: backward-walk replaces streamed cells with single consolidated cell
- Resize reflow: debounced (75ms) re-render of all transcript cells after terminal resize

codex-rs/tui/src/streaming/mod.rs

@@ -70,12 +70,9 @@ impl StreamState {
             .map(|queued| queued.line)
             .collect()
     }
-    /// Drains all queued lines from the front of the queue.
-    pub(crate) fn drain_all(&mut self) -> Vec<Line<'static>> {
-        self.queued_lines
-            .drain(..)
-            .map(|queued| queued.line)
-            .collect()
+    /// Clears queued lines while keeping collector/turn lifecycle state intact.
+    pub(crate) fn clear_queue(&mut self) {
+        self.queued_lines.clear();
     }
     /// Returns whether no lines are queued for commit.
     pub(crate) fn is_idle(&self) -> bool {