feat(batch,extract): default batch to Adaptive Stealth Mode; fall back on REQS007

[AnderRV]

Summary

zenrows batch create sent tasks without mode, so protected sites failed with REQS002 unless the user knew to force --js-render or --premium-proxy. It now uses Adaptive Stealth Mode by default, like fetch and extract.

• batch create: adds mode=auto to every task that doesn't force js_render / premium_proxy or set mode itself. It's applied per task, not job-level, because the API rejects a task that combines a job-level mode=auto with its own js_render or premium_proxy (REQS004). --manual turns it off, and defaultMode: "manual" in config is respected.
• --proxy-country now works without --premium-proxy in auto mode. The standalone job-level check is gone; the per-task check still validates job + task params together.
• batch estimate applies the same rule and counts auto tasks at the 25x upper bound, labelled as such. Note: policy credit caps now see that upper bound, so --manual is the way to get the old count.
• extract now also falls back to Autoparse on REQS007 (domain not prepared for Extract yet), not only AUTH010.
• Help text, the batch-jobs and extract skills, and the batch template README are updated.

Test plan

• npm run typecheck, npm test (283 passing), rebased on 1.3.2
• Live zenrows extract on a domain that returns REQS007: falls back to Autoparse with data
• Live batch estimate: 55 credits with auto vs 7 with --manual for a 3-line spec
• Live batch create --proxy-country us --follow with 2 auto tasks + 1 premium_proxy task: 3/3 successful

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