calibration: surface backtest-cleared loosening proposals in the tuning advisor with evidence payloads

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Problem

computeTuningRecommendations (src/review/auto-tune.ts) still emits loosening advice as prose with NO payload — the advisor and the new backtest-gated loosening loop (#8121 narrow start) don't know about each other, so an operator reading tuning recommendations can't see that a loosening was backtest-cleared (or applied).

Requirements

• A backtest-cleared loosening proposal surfaces as a TuningRec with a payload + the split comparisons as evidence, ranked alongside the tightening recs; an APPLIED loosening surfaces as info.
• The advisor itself still never applies anything — it reports; the apply path stays the flag-gated loop.

Deliverables

• TuningRec integration + tests (evidence rendering, ranking, applied-state reporting)

Links & Resources

#8121 (parent), src/review/auto-tune.ts (computeTuningRecommendations, OverridePayload)
maintainer-only — advisor surface for the autonomous loop.

[linear-code]

JSO-5661