README.md: updated Real browser mode and sidebar agent sections with
model routing, cookie import button, no idle timeout in headed mode.
Updated skill table entries for /browse and /open-gstack-browser.
docs/skills.md: updated /open-gstack-browser deep dive with model
routing and cookie import details.
GSTACK_BROWSER_V0.md: added 6 new SHIPPED items to implementation
status table (model routing, debug logging, idle timeout, cookie
button, arrow hint, architecture doc).
TODOS.md: marked "Sidebar agent Write tool + error visibility" as
SHIPPED. Added new P2 TODO for direct API calls to eliminate
claude -p startup tax.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>