[browser] Extract the generic browser-task engine from the apply loop

[serge-ivo]

[browser] Extract the generic browser-task engine from the apply loop

Factor the job-specific parts out of lib/apply-loop.ts so the pure loop can drive ANY objective, with zero behavior change to job-apply.

Do

• Keep runApplyLoop / ApplyDeps<J extends BrowserJobBase> as the generic core (it already is).
• Move job-specific pieces behind the decide dep + a pluggable prompt: applySystemPrompt, decideAction, and the job-only finish outcomes (submitted/ready/expired/blocked). Introduce a generic outcome set (done/blocked/needs_input/failed/...) the apply variant maps onto.
• No new entry points here — apply keeps calling the same code paths.

Acceptance

• Job-apply behavior + tests unchanged (full apply suite green).
• The generic engine is importable without pulling in job-specific prompt/outcomes.

Part of the browser-generalization epic. Blocks the rest.

[serge-ivo]

Closing as implemented through the browser-task work on main. Evidence: BrowserTaskWorkflow uses the generic runApplyLoop with browser-task-specific prompt/decision in workers/api/src/lib/browser-task-loop.ts, keeping the apply loop reusable without job-specific entry points.

[serge-ivo]

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