Full `nix flake check` (CI) runs the treefmt formatting derivation. While the
hive-ci runner was offline (#1221), PRs merged without it, leaving 5 files
unformatted: hive-ag3nt/src/web_ui.rs, hive-c0re/src/bin/hivectl.rs,
hive-c0re/src/knowledge.rs, hive-c0re/src/matrix.rs,
hive-forge/src/verbs/attachment_get.rs. `nix fmt` output, pure formatting.
hive-c0re now auto-creates the Forgejo push webhook for
internal/knowledge at startup (ensure_webhook). this is what was
missing — the webhook endpoint existed but was never registered in
forgejo, so merging iris's PR didn't trigger a pull.
also adds a periodic hourly pull as a fallback (and an immediate pull
at startup to reconcile commits that landed while c0re was offline).
fixes#1244.
