Security: browser, dotenv, node exec

SSRF after clicks; workspace .env restrictions; sanitized node exec summaries as untrusted system events.

Browser: blocked-destination checks re-run after interaction-driven navigations so SSRF quarantine cannot be bypassed by clicking through to forbidden URLs.
dotenv: runtime-control, browser-control, and skip-server env vars are blocked from untrusted workspace .env files.
Gateway/node: exec.started / finished / denied from remote nodes are treated as untrusted and sanitized before they can become trusted System: content.