homura: named OMP tasks, visible model errors, read-only workspaces #43

Pin omp-manager 1bbf27cc5262dd99cc3f71f173930d7ee3107fd8 and bind /var/lib/omp-manager/workspaces read-only at /mnt/omp-tasks inside coral/reef. New tasks require a concise name separate from their goal; picker and yield wakes use names without copying full goals. Empty model errors and aborts remain inspectable through polling/restart/recovery. Manager changes authored by OMP workers and independently integrated/reviewed. Verification: TypeScript check; 22/22 tests; Go tests/race/vet; Nix manager/picker/image-context builds; real pinned OMP terminal/RPC/error-recovery fixture; full homura system derivation evaluation and exact read-only mount assertion. No host rebuild or live mount claimed.