Fix real-time build log streaming and scroll behavior

- Use line-by-line reading for Docker build output instead of io.Copy
  to ensure each log line is written immediately without buffering
- Add isNearBottom() helper to check scroll position before auto-scroll
- Only auto-scroll logs if user was already near bottom (better UX)
- Use requestAnimationFrame for smoother scroll-to-bottom animation

internal/docker/client.go

@@ -2,6 +2,7 @@
 package docker
 
 import (
+	"bufio"
 	"context"
 	"errors"
 	"fmt"
@@ -489,15 +490,10 @@ func (c *Client) performBuild(
 		}
 	}()
 
-	// Read build output - write to stdout and optional log writer
-	var output io.Writer = os.Stdout
-	if opts.LogWriter != nil {
-		output = io.MultiWriter(os.Stdout, opts.LogWriter)
-	}
-
-	_, err = io.Copy(output, resp.Body)
+	// Stream build output line by line for real-time log updates
+	err = c.streamBuildOutput(resp.Body, opts.LogWriter)
 	if err != nil {
-		return "", fmt.Errorf("failed to read build output: %w", err)
+		return "", err
 	}
 
 	// Get image ID
@@ -513,6 +509,41 @@ func (c *Client) performBuild(
 	return "", nil
 }
 
+// scannerInitialBufferSize is the initial buffer size for the build log scanner.
+const scannerInitialBufferSize = 64 * 1024 // 64KB
+
+// scannerMaxBufferSize is the max buffer size for build log lines (base64 layers can be large).
+const scannerMaxBufferSize = 1024 * 1024 // 1MB
+
+// streamBuildOutput reads Docker build output line by line and writes to stdout and optional log writer.
+// Docker sends newline-delimited JSON, so reading line by line ensures each log entry is written immediately.
+func (c *Client) streamBuildOutput(body io.Reader, logWriter io.Writer) error {
+	scanner := bufio.NewScanner(body)
+	buf := make([]byte, 0, scannerInitialBufferSize)
+	scanner.Buffer(buf, scannerMaxBufferSize)
+
+	newline := []byte{'\n'}
+
+	for scanner.Scan() {
+		line := scanner.Bytes()
+		// Write to stdout
+		_, _ = os.Stdout.Write(line)
+		_, _ = os.Stdout.Write(newline)
+		// Write to log writer if provided
+		if logWriter != nil {
+			_, _ = logWriter.Write(line)
+			_, _ = logWriter.Write(newline)
+		}
+	}
+
+	scanErr := scanner.Err()
+	if scanErr != nil {
+		return fmt.Errorf("failed to read build output: %w", scanErr)
+	}
+
+	return nil
+}
+
 func (c *Client) performClone(ctx context.Context, cfg *cloneConfig) (*CloneResult, error) {
 	// Create work directory for clone destination
 	err := os.MkdirAll(cfg.containerDir, workDirPermissions)