One-command sandbox: `banger vm run` on a fresh host now Just Works.
No prior `banger image pull` or `banger kernel pull` needed.
Changes:
- Default `default_image_name` flips from "default" to "debian-bookworm"
so the golden image is the implicit target when `--image` is omitted.
- `CreateVM` resolves the image via a new `findOrAutoPullImage`: try
the local store first, and on miss fall back to the embedded imagecat
catalog + auto-pull. Emits a vm-create progress stage so the user
sees "pulling from image catalog" in the create output.
- `resolveKernelInputs` gains context + the same pattern via
`readOrAutoPullKernel`: try the local kernelcat, and on miss look up
the embedded kernelcat and auto-pull. Fires whenever a bundle's
manifest references a kernel the user hasn't pulled yet, not just
during image pull — any CreateVM with an image that needs a kernel
not yet local will resolve it.
- `--image` help text updated on both `vm run` and `vm create`.
Six tests cover local-hit-no-pull, auto-pull-on-miss, not-in-catalog
error propagation, and a non-ENOENT kernel read error does NOT trigger
a misleading "not in catalog" claim.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>