Part B (c0re half). New forge/ci_runner.rs: validate the hive-ci runner's
persisted .runner against the forge (GET /admin/runners/{id}); if absent or
stale, mint a fresh registration token (GET /admin/runners/registration-token,
raw request against the local http forge — forgejo-api 0.11 doesn't wrap it)
and hand it to hive-priv's RegisterCiRunner to write the host env-file +
restart the runner. Gated on HYPERHIVE_FORGE_CI_ENABLED; best-effort (never
aborts the startup sweep). Called from ensure_all after the org/repo seeding.
The nix boot-path change (drop prefetch gating, add runner precond, set the
env var) lands next on this branch.
2941a889f0