[browser] BrowserTaskWorkflow + objective-driven system prompt #71

[browser] BrowserTaskWorkflow + objective-driven system prompt

A generic Cloudflare Workflow mirroring JobApplyWorkflow (workflows/job-apply.ts) that drives the browser toward an arbitrary {objective, url} using the generic engine (from the extraction issue) + the same /browser/* runner primitives + the same handoff machinery.

Do

• New BrowserTaskWorkflow class + [[workflows]] binding in wrangler.toml.
• Generic objective-driven system prompt (replaces the ~1900-line job prompt): "achieve this objective on this page; act one step at a time; hand off on captcha/2FA/ambiguity."
• Reuse captcha/stuck/needs_input handoffs verbatim.
• Sensitive-action gate: default human-approval before send/pay/delete/post/irreversible clicks.

Acceptance

• Workflow runs the generic loop end-to-end against a test page (dry-run харness).
• Handoffs (captcha/stuck/needs_input) work identically to apply.
• Sensitive actions require approval by default.

Depends on the engine extraction. Part of the browser-generalization epic.