Reuse the committed quota capture in native benchmark preflight - #8259

A native heartbeat checkpoint preflight captured the complete quota decision, read the full CLI view over stdout, and wrote that view again for SessionStart. The preflight now requests the existing prepared capture reference and binds the native read to the committed decision bytes. A mismatched digest aborts before model entry. The native reader still selects its delivery after SessionStart, and context-off preflight retains its full view.

This is the standalone mainline proposal for #8251. The required quota capture route already ships in #8100. The research integration continues to use its independently pinned source.

Validation

• The benchmark checkpoint, progressive-context, research-capture, and native handoff suite passed 100 cases with 38 platform or optional-runtime skips.
• On the proposed head, the focused tests passed for direct capture reuse and digest mismatch rejection. They check the exact native read target and absence of a second view file in the selected path.
• Risk-selected premerge executed five direct checks and nine canaries with zero failures. The benchmark-sensitive maintainer-review hold remains.
• The exact four source and test files passed public-boundary and Ruff checks. Live model cost and benchmark outcomes require separate qualification.