feat: v0.1.6 — watch mode, webhooks (Discord/Slack auto-format)

Watch mode:
- --watch polls a URL at --watch-interval (default 5min)
- Reports diffs to stdout when content changes
- --on-change runs a command with diff JSON on stdin
- Ctrl+C stops cleanly

Webhooks:
- --webhook POSTs JSON on crawl/batch complete and watch changes
- Auto-detects Discord and Slack URLs, formats as embeds/blocks
- Also available via WEBCLAW_WEBHOOK_URL env var
- Non-blocking, errors logged to stderr

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -3,6 +3,16 @@
 All notable changes to webclaw are documented here.
 Format follows [Keep a Changelog](https://keepachangelog.com/).
 
+## [0.1.6] — 2026-03-26
+
+### Added
+- `--watch`: monitor a URL for changes at a configurable interval with diff output
+- `--watch-interval`: seconds between checks (default: 300)
+- `--on-change`: run a command when changes are detected (diff JSON piped to stdin)
+- `--webhook`: POST JSON notifications on crawl/batch complete and watch changes. Auto-formats for Discord and Slack webhooks
+
+---
+
 ## [0.1.5] — 2026-03-26
 
 ### Added