fix(screentracker): address round 2 review feedback

- Drop hardcoded '1s' from writeStabilizeEchoTimeout comment so
  it won't go stale if the stability check duration changes
- Replace em-dashes (U+2014) with periods in four comments
- Use Phase 1/Phase 2 vocabulary in inline comments to match
  the doc comment on writeStabilize
- Replace loop-and-flag with slices.ContainsFunc in test

Author: johnstcn

lib/screentracker/pty_conversation.go

@@ -20,7 +20,7 @@ import (
 const (
 	// writeStabilizeEchoTimeout is the timeout for the echo
 	// detection WaitFor loop in writeStabilize Phase 1. The
-	// effective ceiling may be slightly longer because the 1s
+	// effective ceiling may be slightly longer because the
 	// stability check inside the condition runs outside
 	// WaitFor's timeout select. Non-echoing agents (e.g. TUI
 	// agents using bracketed paste) will hit this timeout,
@@ -438,12 +438,12 @@ func (c *PTYConversation) sendMessage(ctx context.Context, messageParts ...Messa
 // Phase 1 (echo detection): writes the message text and waits
 // for the screen to change and stabilize. This detects agents
 // that echo typed input. If the screen doesn't change within
-// writeStabilizeEchoTimeout, this is non-fatal — many TUI
+// writeStabilizeEchoTimeout, this is non-fatal. Many TUI
 // agents buffer bracketed-paste input without rendering it.
 //
 // Phase 2 (processing detection): writes a carriage return
 // and waits for the screen to change, indicating the agent
-// started processing. This phase is fatal on timeout — if the
+// started processing. This phase is fatal on timeout: if the
 // agent doesn't react to Enter, it's unresponsive.
 func (c *PTYConversation) writeStabilize(ctx context.Context, messageParts ...MessagePart) error {
 	screenBeforeMessage := c.cfg.AgentIO.ReadScreen()
@@ -452,7 +452,8 @@ func (c *PTYConversation) writeStabilize(ctx context.Context, messageParts ...Me
 			return xerrors.Errorf("failed to write message part: %w", err)
 		}
 	}
-	// wait for the screen to stabilize after the message is written
+	// Phase 1: wait for the screen to stabilize after the
+	// message is written (echo detection).
 	if err := util.WaitFor(ctx, util.WaitTimeout{
 		Timeout:     writeStabilizeEchoTimeout,
 		MinInterval: 50 * time.Millisecond,
@@ -488,7 +489,8 @@ func (c *PTYConversation) writeStabilize(ctx context.Context, messageParts ...Me
 		)
 	}
 
-	// wait for the screen to change after the carriage return is written
+	// Phase 2: wait for the screen to change after the
+	// carriage return is written (processing detection).
 	screenBeforeCarriageReturn := c.cfg.AgentIO.ReadScreen()
 	lastCarriageReturnTime := time.Time{}
 	if err := util.WaitFor(ctx, util.WaitTimeout{

lib/screentracker/pty_conversation_test.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"log/slog"
 	"os"
+	"slices"
 	"sync"
 	"sync/atomic"
 	"testing"
@@ -473,21 +474,16 @@ func TestMessages(t *testing.T) {
 		// Then: Send succeeds and the user message is recorded.
 		msgs := c.Messages()
 		require.True(t, len(msgs) >= 2)
-		var foundUserMsg bool
-		for _, msg := range msgs {
-			if msg.Role == st.ConversationRoleUser && msg.Message == "hello" {
-				foundUserMsg = true
-				break
-			}
-		}
-		assert.True(t, foundUserMsg, "expected user message 'hello' in conversation")
+		assert.True(t, slices.ContainsFunc(msgs, func(m st.ConversationMessage) bool {
+			return m.Role == st.ConversationRoleUser && m.Message == "hello"
+		}), "expected user message 'hello' in conversation")
 	})
 
 	t.Run("send-message-no-echo-no-react", func(t *testing.T) {
 		ctx, cancel := context.WithTimeout(context.Background(), testTimeout)
 		t.Cleanup(cancel)
 
-		// Given: an agent that is completely unresponsive — it
+		// Given: an agent that is completely unresponsive. It
 		// neither echoes input nor reacts to carriage return.
 		c, _, mClock := newConversation(ctx, t, func(cfg *st.PTYConversationConfig) {
 			a := &testAgent{screen: "prompt"}
@@ -516,7 +512,7 @@ func TestMessages(t *testing.T) {
 	t.Run("send-message-no-echo-context-cancelled", func(t *testing.T) {
 		// Given: a non-echoing agent and a cancellable context.
 		// The onWrite signals when writeStabilize starts writing
-		// message parts — this is used to synchronize the cancel.
+		// message parts. This is used to synchronize the cancel.
 		sendCtx, sendCancel := context.WithCancel(context.Background())
 		t.Cleanup(sendCancel)