refactor(adapter): split browser command signatures

[jackwener]

Summary

• split adapter func typing by browser runtime: browser commands receive page, non-browser commands receive args directly
• remove dead _page parameters from non-browser adapters, scaffold, docs, and direct adapter tests
• add BasePage.fetchJson() as the narrow browser-context JSON fetch primitive and route pipeline single browser fetches through it

Verification

• npm run typecheck
• npm run build
• OPENCLI_DAEMON_PORT=29125 npm test