Chip tab data: the signed silicon runs index, written by t27c and cited by a spec #7738

Part of epic #6655. Follows #7723 (t27c run-record --json) and pairs with gHashTag/trinity#1527, the Chip tab that renders it.

Goal

The Spec Explorer's Chip tab gets the signed silicon runs as data that t27c wrote. A spec cites that data so the trinity sync vendors it.

Boundary

• docs/reports/silicon-runs/index.json: a JSON array of t27c run-record --json documents, unchanged.
• specs/verified/silicon_runs.t27 (new): the citation, carrying SOURCES and the exact commands that produced each entry.
• Its seal.
• No code change.

User Scenarios & Testing

• Given the index, the R3-2 entry is complete, FRESH, Die NAMED and citable. The R3-3 entry is RUN_TOO_FEW_RECEIPTS until dies B and C report.

Requirements

• FR-1: every entry is produced by a master build of t27c; judged_by names it.
• FR-2: the citation states which seal each entry was judged against.

Success Criteria

• t27c test-report specs/verified/silicon_runs.t27: all pass, 0 vacuous.
• t27c seal specs/verified/silicon_runs.t27 --verify: all hashes MATCH.