Repointing the production hub's 50 Gitea-hosted federation sources to Forgejo
ahead of the 2026-08-31 CoulombCore retirement took /v1/federated to HTTP 500.
One member index (evidence-binder) has capability rows with no `id`, and
compose_federated_index dereferenced item["id"] unguarded. Its Gitea copy was a
stale snapshot returning a non-mapping, so those rows had never been parsed.
A single malformed member index must not take down the whole endpoint. Extract
_read_index_entries(): unparseable YAML, a non-mapping body, an empty file, and
a non-list `capabilities` each degrade to a warning and an empty row list, and
rows without an `id` are skipped individually. A failed source stays listed with
count 0 so it remains visible to operators rather than silently disappearing.
Also fix wall-clock rot in tests/test_plan_check.py, which was already failing
at clean HEAD: three tests pinned the compose date to a literal that has now
aged past STALE_DAYS.
Add workplan REUSE-WP-0020 covering the full cutover.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>