Captures a lesson from this session: "no browser in this container"
usually means no browser pre-installed, not unreachable. nixpkgs#chromium
is a `nix shell` away and one headless invocation renders a page +
writes a PNG, no puppeteer/playwright needed for a static screenshot.
Every agent hits "I have no browser" sooner or later when reviewing a
frontend change; this has been rediscovered independently across
several sessions rather than remembered. Belongs in base (every agent
needs it, not role-specific) alongside the sibling skills already
there.
