#1920 r14: a result without usage passes native completion unmarked

[realmarcin]

Codex round 14 on PR #1920 (head 86caf26), must-fix. A result with no usage key finalizes nothing and sets no marker, so the controller completes on snapshot totals (deleting the v10q result's usage in memory turns 118,696 into 344 with no qualifier). Record terminal results without usage under a marker, require usable finalized usage for native completion, and qualify the basis wording. Fix in #1920.

[realmarcin]

Fixed in acc3ead on PR #1920: a result with no usage is counted under terminal_results_without_usage (whitelisted, with a basis sentence); the controller's completion gate refuses an observation without usage_from_terminal_result; the basis requires a result carrying complete usage. Closes when #1920 merges.