feat: join audit-storage usage without inventing a booked Scaleway fact

Ingest resource-control's August technical usage, omit nulls, and
reconcile forecast + usage + booked facts. Commissioning month reports
missing_booked_fact instead of 0.00. T05 still waits on the first invoice.

docs/evidence/fin-wp-0004-t05-commissioning-2026-08.md

@@ -0,0 +1,45 @@
+# FIN-WP-0004-T05 — commissioning-period join, 2026-08
+
+Date: 2026-08-15
+Resource: `resource:platform:audit-storage`
+Attribution key: `platform:audit-storage`
+
+## What exists
+
+| Record | Count | Authority |
+| --- | --- | --- |
+| Forecast (base, 2026-09 … 2027-08) | 12 rows | resource-control |
+| Technical usage 2026-08 | 1 row | resource-control |
+| Booked Scaleway fact 2026-08 | **0** | fin-hub |
+
+The object store was commissioned 2026-08-14. resource-control’s usage
+record carries `infrastructure_eur: null` and names fin-hub as the
+owner of that gap. There is no invoice. A null is not booked as 0.00.
+
+## Join result
+
+`ingest_resource_usage` stores only measured quantities (`database_gb`,
+`stored_gb`, `backup_success_pct`, `restore_rto_minutes`). Null usage
+fields and the missing infrastructure amount remain gaps in
+`source_evidence`.
+
+`reconcile_resource_period` for 2026-08 reports:
+
+- usage present
+- `missing_booked_fact: true`
+- `booked_effective_amount: null`
+- `invented_zero: false`
+
+`exchange_health` raises `usage_without_booked_fact` for this period.
+
+## Why T05 stays open
+
+The done criterion is: the same cost booked once, projected,
+joined to technical evidence, and returned without a second ledger.
+That cost does not exist yet. The first comparable Scaleway invoice
+period is 2026-09. This note is the commissioning baseline, not
+closure.
+
+When a provider charge or credit lands, book it once, bind
+`financial_fact_id` → `resource:platform:audit-storage`, and rerun
+`ledger reconcile-resource --period 2026-09`.