fix(health): name scoring-job index migrations in the as-built map

[cursor]

Why

PR #131 classifies expired scoring-job leases, but the TRACEABILITY migrations/ tree still ended at 0012 and docs/architecture/AS_BUILT_SCHEMA.md had no Active-PR note for 0020/0021/0022. Reviewers would treat that tree as the physical inventory and miss the product apply path.

This branch is #131 at 8c51e3d plus the inventory and millisecond-rounding repair. Prefer this head over merging #82, #113, or #131 alone.

TDD

RED: active_backlog_health_indexes_are_named_in_the_physical_inventory failed because the TRACEABILITY tree did not name 0020_backlog_health_indexes.sql.

GREEN: the tree and as-built map name 0020/0021/0022 as Active PR evidence, not protected-main truth.

What changed

• name 0020, 0021, and 0022 in the TRACEABILITY migrations tree;
• add the Active-PR operational-backlog index paragraph to docs/architecture/AS_BUILT_SCHEMA.md;
• point capability-health and risk/quality evidence at feat(health): observe expired scoring-job leases #131 / HTTP test(health): cover accept ConnectionReset and postgres drop #122;
• round EXTRACT(EPOCH) millisecond conversions so a 0.6 ms created_at becomes 1 instead of truncating to an invalid stored time.

Verification

• cargo test --test documentation_architecture_contract (11/11);
• cargo fmt and cargo clippy --all-targets -- -D warnings.

The fractional-millisecond PostgreSQL case is in tests/postgres_scoring_job_backlog_health.rs for exact-head CI (TEST_DATABASE_URL is not available in this writer environment).

Coordination

• Prefer this head over feat(health): observe PostgreSQL operational backlogs #82, feat(health): observe PostgreSQL scoring-job backlogs #113, and feat(health): observe expired scoring-job leases #131.
• Draft feat(identity): persist append-only account-link history #114 must keep its identity-link migration number after 0022.
• HTTP probes remain test(health): cover accept ConnectionReset and postgres drop #122. Do not self-approve.