feat: sync agent-browser skill with upstream vercel-labs/agent-browser

Update SKILL.md to match the latest upstream skill from
vercel-labs/agent-browser, adding substantial new capabilities:

- Authentication (auth vault, profiles, session persistence, state files)
- Command chaining, annotated screenshots, diffing
- Security features (content boundaries, domain allowlist, action policy)
- iOS Simulator support, Lightpanda engine, downloads, clipboard
- JS eval improvements (--stdin, -b for shell safety)
- Timeout guidance, config files, session cleanup

Add 7 reference docs (commands, authentication, snapshot-refs,
session-management, video-recording, profiling, proxy-support) and
3 ready-to-use shell templates.

Kept our YAML frontmatter, setup check section, and Playwright MCP
comparison table which are unique to our plugin context.

plugins/compound-engineering/skills/agent-browser/templates/capture-workflow.sh

@@ -0,0 +1,69 @@
+#!/bin/bash
+# Template: Content Capture Workflow
+# Purpose: Extract content from web pages (text, screenshots, PDF)
+# Usage: ./capture-workflow.sh <url> [output-dir]
+#
+# Outputs:
+#   - page-full.png: Full page screenshot
+#   - page-structure.txt: Page element structure with refs
+#   - page-text.txt: All text content
+#   - page.pdf: PDF version
+#
+# Optional: Load auth state for protected pages
+
+set -euo pipefail
+
+TARGET_URL="${1:?Usage: $0 <url> [output-dir]}"
+OUTPUT_DIR="${2:-.}"
+
+echo "Capturing: $TARGET_URL"
+mkdir -p "$OUTPUT_DIR"
+
+# Optional: Load authentication state
+# if [[ -f "./auth-state.json" ]]; then
+#     echo "Loading authentication state..."
+#     agent-browser state load "./auth-state.json"
+# fi
+
+# Navigate to target
+agent-browser open "$TARGET_URL"
+agent-browser wait --load networkidle
+
+# Get metadata
+TITLE=$(agent-browser get title)
+URL=$(agent-browser get url)
+echo "Title: $TITLE"
+echo "URL: $URL"
+
+# Capture full page screenshot
+agent-browser screenshot --full "$OUTPUT_DIR/page-full.png"
+echo "Saved: $OUTPUT_DIR/page-full.png"
+
+# Get page structure with refs
+agent-browser snapshot -i > "$OUTPUT_DIR/page-structure.txt"
+echo "Saved: $OUTPUT_DIR/page-structure.txt"
+
+# Extract all text content
+agent-browser get text body > "$OUTPUT_DIR/page-text.txt"
+echo "Saved: $OUTPUT_DIR/page-text.txt"
+
+# Save as PDF
+agent-browser pdf "$OUTPUT_DIR/page.pdf"
+echo "Saved: $OUTPUT_DIR/page.pdf"
+
+# Optional: Extract specific elements using refs from structure
+# agent-browser get text @e5 > "$OUTPUT_DIR/main-content.txt"
+
+# Optional: Handle infinite scroll pages
+# for i in {1..5}; do
+#     agent-browser scroll down 1000
+#     agent-browser wait 1000
+# done
+# agent-browser screenshot --full "$OUTPUT_DIR/page-scrolled.png"
+
+# Cleanup
+agent-browser close
+
+echo ""
+echo "Capture complete:"
+ls -la "$OUTPUT_DIR"