Surface job cost (estimate pre-run, actual post-run) — leverage new ep costs / .ep format

[johnjosephhorton]

Summary

There is no cost estimate or cost summary anywhere in the zwill CLI, even though the workflow guardrails emphasize showing likely cost before spending:

Do not run costly EDSL jobs until the user has seen the plan, prediction count, model list, and likely cost/time risk.

zwill gives you the prediction count but never a dollar/credit figure — not before the run, not after. edsl-run has --dry-run (validates the job) but does not price it, and its completion output contains no cost line. The only way to recover actual cost is to decompress the raw results and reverse-engineer it from response_probabilities_one_usd_buys in the model responses.

What I had to do this session

To calibrate cost before authorizing a ~2000-call run, I ran a 3-call smoke test, then decompressed *_results.json.gz and computed 1 / response_probabilities_one_usd_buys per row to get ~$0.0165/call → ~$33 projected. This worked but shouldn't be necessary.

Opportunity: the new ep CLI already does this

The ep CLI (EDSL) exposes native cost tracking that zwill could wrap or adopt:

ep costs            # Track estimated and actual job costs
  ep costs log --output costs.jsonl --estimated 1.25 --model gpt-4o --agents 10 --questions 5
  ep costs log --output costs.jsonl --actual-from results.ep --note "pilot run"
  ep results cost results.ep

There is also a .ep package format (results.ep, survey.ep, agent_list.ep, jobs.ep) with ep metadata / ep inspect / ep results cost. If zwill emitted/consumed .ep artifacts (or shelled out to ep costs/ep results cost), cost could become first-class.

Suggested fixes

• Print an estimated cost alongside the prediction count at export/approve time (via ep costs-style estimation).
• Print actual cost in the edsl-run completion envelope and in twin-results import (via ep results cost / --actual-from results.ep).
• Consider adopting the .ep package format for exported jobs and imported results so ep costs/ep results cost/ep metadata work directly against zwill artifacts.