Implement full snapshot lifecycle: pause (snapshot + free resources),
resume (UFFD-based lazy restore), and named snapshot templates that
can spawn new sandboxes from frozen VM state.
Key changes:
- Snapshot header system with generational diff mapping (inspired by e2b)
- UFFD server for lazy page fault handling during snapshot restore
- Stable rootfs symlink path (/tmp/fc-vm/) for snapshot compatibility
- Templates DB table and CRUD API endpoints (POST/GET/DELETE /v1/snapshots)
- CreateSnapshot/DeleteSnapshot RPCs in hostagent proto
- Reconciler excludes paused sandboxes (expected absent from host agent)
- Snapshot templates lock vcpus/memory to baked-in values
- Proper cleanup of uffd sockets and pause snapshot files on destroy
Implements Phase 1: boot a Firecracker microVM, execute a command inside
it via envd, and get the output back. Uses raw Firecracker HTTP API via
Unix socket (not the Go SDK) for full control over the VM lifecycle.
- internal/vm: VM manager with create/pause/resume/destroy, Firecracker
HTTP client, process launcher with unshare + ip netns exec isolation
- internal/network: per-sandbox network namespace with veth pair, TAP
device, NAT rules, and IP forwarding
- internal/envdclient: Connect RPC client for envd process/filesystem
services with health check retry
- cmd/host-agent: demo binary that boots a VM, runs "echo hello", prints
output, and cleans up
- proto/envd: canonical proto files with buf + protoc-gen-connect-go
code generation
- images/wrenn-init.sh: minimal PID 1 init script for guest VMs
- CLAUDE.md: updated architecture to reflect TAP networking (not vsock)
and Firecracker HTTP API (not Go SDK)
