[browser] BrowserTaskWorkflow + objective-driven system prompt

[serge-ivo]

[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.

[serge-ivo]

Closing as implemented on main. Evidence: commit 9303abb adds BrowserTaskWorkflow, wrangler/index exports it, browser-task-loop.ts provides the objective-driven prompt/tools, and the workflow reuses apply handoffs for captcha/stuck/needs_input.

[serge-ivo]

Implementation links: no associated PR was found; this landed direct on main in 9303abb.