Load Alpine's CSP build so the UI's directives run (closes #371)

Every page's Content-Security-Policy forbids eval, which the standard Alpine.js build needs, so no directive ran in a browser: both add forms on the webhook page showed open, and events in the event log could not be collapsed. The UI now loads Alpine's CSP build (@alpinejs/csp 3.14.9 in 3p/); the policy is unchanged. Each directive names a property or method of a component registered in static/js/app.js (collapsible, targetForm), and each card holds its own x-data. A browser test, built only with the browser tag, loads the webhook page and the event log under the real headers; make test-browser runs it in Docker. New test-only dependency chromedp, which raises golang.org/x/sys to 0.47.0.

Model: opus-5-5

Makefile

@@ -1,4 +1,4 @@
-.PHONY: bootstrap setup assets test lint fmt fmt-check check build run dev deps docker clean hooks css version
+.PHONY: bootstrap setup assets test test-browser lint fmt fmt-check check build run dev deps docker clean hooks css version
 
 # Default target
 .DEFAULT_GOAL := check
@@ -33,6 +33,9 @@ assets:
 test:
 	@script/test
 
+test-browser:
+	@script/test-browser
+
 lint:
 	@script/lint