t27c frontier --audit: rerun a sample of reused verdicts (glue for verdict_audit.t27) #8556

The glue for specs/verified/verdict_audit.t27 (#8542, merged in #8543).

t27c frontier --audit <round> reruns the REUSE specs that audit_pick(spec hash word, round) selects, about 1 in 16 per round, with test-report in process. It prints agrees or POISONED for each spec and exits 1 when any verdict disagrees with its rerun (audit_result). The seal lookup that decide used inline becomes one seal_of function that both share.

Hand-written lines are paid for by deleting the dead one-shot scripts/gen_w367.py.

The PR also adds the t27b ledger row that specs/compiler/zig_shadow_initializer.t27 (#8418) left UNLISTED. CI measured it as pass.

Acceptance criteria

• t27c frontier --audit N prints one line per audited spec and exits 1 only when one is POISONED.
• A real round on master is recorded in the PR with its counts and time.
• Hand-written foreign lines do not grow (own-language gate green).

Boundary

bootstrap/src/service.rs
bootstrap/src/main.rs
bootstrap/gen/rust/verified/verdict_audit.rs
docs/reports/t27b_expectations.json
scripts/gen_w367.py

User Scenarios

• Given a completed frontier round N with reused verdicts, when running t27c frontier --audit N, then the command reruns approximately 1 in 16 REUSE specs selected by audit_pick, prints "agrees" or "POISONED" per spec, and exits 1 if any verdict disagrees with its rerun.

Requirements

• FR-001: t27c frontier --audit <round> MUST rerun REUSE specs selected by audit_pick(spec hash word, round) at approximately 1 in 16 sampling rate
• FR-002: The command MUST print one line per audited spec showing "agrees" or "POISONED"
• FR-003: The command MUST exit with code 1 when any audited verdict disagrees with its rerun (audit_result), otherwise exit 0
• FR-004: The seal lookup used by decide MUST be refactored into a shared seal_of function
• FR-005: The dead script scripts/gen_w367.py MUST be deleted
• FR-006: The t27b ledger row for specs/compiler/zig_shadow_initializer.t27 MUST be added to docs/reports/t27b_expectations.json

Success Criteria

• t27c frontier --audit 1 prints one line per audited spec and exits 0 when all agree
• t27c frontier --audit 1 exits 1 when any spec shows "POISONED"
• The command completes within 30 seconds for a typical round
• Hand-written foreign lines do not increase (own-language gate passes)
• A real round on master is recorded with counts and time