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/references/video-recording.md

@@ -0,0 +1,173 @@
+# Video Recording
+
+Capture browser automation as video for debugging, documentation, or verification.
+
+**Related**: [commands.md](commands.md) for full command reference, [SKILL.md](../SKILL.md) for quick start.
+
+## Contents
+
+- [Basic Recording](#basic-recording)
+- [Recording Commands](#recording-commands)
+- [Use Cases](#use-cases)
+- [Best Practices](#best-practices)
+- [Output Format](#output-format)
+- [Limitations](#limitations)
+
+## Basic Recording
+
+```bash
+# Start recording
+agent-browser record start ./demo.webm
+
+# Perform actions
+agent-browser open https://example.com
+agent-browser snapshot -i
+agent-browser click @e1
+agent-browser fill @e2 "test input"
+
+# Stop and save
+agent-browser record stop
+```
+
+## Recording Commands
+
+```bash
+# Start recording to file
+agent-browser record start ./output.webm
+
+# Stop current recording
+agent-browser record stop
+
+# Restart with new file (stops current + starts new)
+agent-browser record restart ./take2.webm
+```
+
+## Use Cases
+
+### Debugging Failed Automation
+
+```bash
+#!/bin/bash
+# Record automation for debugging
+
+agent-browser record start ./debug-$(date +%Y%m%d-%H%M%S).webm
+
+# Run your automation
+agent-browser open https://app.example.com
+agent-browser snapshot -i
+agent-browser click @e1 || {
+    echo "Click failed - check recording"
+    agent-browser record stop
+    exit 1
+}
+
+agent-browser record stop
+```
+
+### Documentation Generation
+
+```bash
+#!/bin/bash
+# Record workflow for documentation
+
+agent-browser record start ./docs/how-to-login.webm
+
+agent-browser open https://app.example.com/login
+agent-browser wait 1000  # Pause for visibility
+
+agent-browser snapshot -i
+agent-browser fill @e1 "demo@example.com"
+agent-browser wait 500
+
+agent-browser fill @e2 "password"
+agent-browser wait 500
+
+agent-browser click @e3
+agent-browser wait --load networkidle
+agent-browser wait 1000  # Show result
+
+agent-browser record stop
+```
+
+### CI/CD Test Evidence
+
+```bash
+#!/bin/bash
+# Record E2E test runs for CI artifacts
+
+TEST_NAME="${1:-e2e-test}"
+RECORDING_DIR="./test-recordings"
+mkdir -p "$RECORDING_DIR"
+
+agent-browser record start "$RECORDING_DIR/$TEST_NAME-$(date +%s).webm"
+
+# Run test
+if run_e2e_test; then
+    echo "Test passed"
+else
+    echo "Test failed - recording saved"
+fi
+
+agent-browser record stop
+```
+
+## Best Practices
+
+### 1. Add Pauses for Clarity
+
+```bash
+# Slow down for human viewing
+agent-browser click @e1
+agent-browser wait 500  # Let viewer see result
+```
+
+### 2. Use Descriptive Filenames
+
+```bash
+# Include context in filename
+agent-browser record start ./recordings/login-flow-2024-01-15.webm
+agent-browser record start ./recordings/checkout-test-run-42.webm
+```
+
+### 3. Handle Recording in Error Cases
+
+```bash
+#!/bin/bash
+set -e
+
+cleanup() {
+    agent-browser record stop 2>/dev/null || true
+    agent-browser close 2>/dev/null || true
+}
+trap cleanup EXIT
+
+agent-browser record start ./automation.webm
+# ... automation steps ...
+```
+
+### 4. Combine with Screenshots
+
+```bash
+# Record video AND capture key frames
+agent-browser record start ./flow.webm
+
+agent-browser open https://example.com
+agent-browser screenshot ./screenshots/step1-homepage.png
+
+agent-browser click @e1
+agent-browser screenshot ./screenshots/step2-after-click.png
+
+agent-browser record stop
+```
+
+## Output Format
+
+- Default format: WebM (VP8/VP9 codec)
+- Compatible with all modern browsers and video players
+- Compressed but high quality
+
+## Limitations
+
+- Recording adds slight overhead to automation
+- Large recordings can consume significant disk space
+- Some headless environments may have codec limitations