[Track] Gate D live conformance expansion and trend discipline

[SMC17]

Goal

Make live conformance evidence sustainable and decision-grade.

Deliverables

• Extend Gate D checks as live method coverage grows.
• Keep trend summaries and thresholds actionable.
• Improve artifact clarity for run-to-run diagnosis.

Acceptance

• scripts/gates/gate_d.sh and trend merge script enforce agreed thresholds.
• Artifacts clearly show pass/fail reason and method-level evidence.
• 7-day trend outputs are consumed in release decision workflow.

Linked Epic

• [Vision Epic] Agent-native XRP Ledger daemon in Zig: execution program #4

[SMC17]

Child delivery queue: #19 (good first issue), #20 (good first issue). Suggested order: #20 -> #19.

[SMC17]

New child issues for this track: #35 (Gate D trend metrics for ping/ledger_current), #36 (Gate D artifact schema validation). #19 and #20 are complete.