Surface unpriced status in human compare and bucketed summary output

[willwashburn]

Follow-up to #510 and #524.

Structured reports expose the underlying gaps: compare cells publish turns versus pricedTurns, and summary buckets publish unpricedTurns. The human presenters still need an explicit unpriced indicator:

• burn compare can print a model total as $0.00 even when its cells have turns > pricedTurns.
• burn summary --bucket prints bucket cost without noting nonzero unpricedTurns.

Add a concise human warning/marker using the existing structured signals. Keep JSON and CSV schemas stable unless a separate schema need is demonstrated.

[willwashburn]

When updating the human renderer, prefer printing the resolved absolute active ledger-home override path rather than a placeholder; the query layer already derives pricing from burn_path().parent().