feat(vm): boot sandboxes from ext4 root disks (#1263)

* feat(vm): boot sandboxes from ext4 root disks

* feat(vm): boot sandboxes with writable overlay disk

* fix(sandbox): improve sandbox provisioning behavior

* fix(vm): repair sandbox image provisioning

* fix(vm): clean up rebase fallout

* perf(vm): cache empty overlay images

* perf(vm): skip repeated sandbox ownership repair

* fix(vm): address lifecycle review issues

* fix(vm): repair gateway vm startup

* wip

Author: drew

.github/workflows/driver-vm-linux.yml

@@ -162,7 +162,7 @@ jobs:
       - name: Verify embedded driver inputs
         run: |
           set -euo pipefail
-          for file in libkrun.so.zst libkrunfw.so.5.zst gvproxy.zst openshell-sandbox.zst; do
+          for file in libkrun.so.zst libkrunfw.so.5.zst gvproxy.zst umoci.zst openshell-sandbox.zst; do
             test -s "target/vm-runtime-compressed/${file}"
           done
 

.github/workflows/driver-vm-macos.yml

@@ -199,7 +199,7 @@ jobs:
       - name: Verify embedded driver inputs
         run: |
           set -euo pipefail
-          for file in libkrun.dylib.zst libkrunfw.5.dylib.zst gvproxy.zst openshell-sandbox.zst; do
+          for file in libkrun.dylib.zst libkrunfw.5.dylib.zst gvproxy.zst umoci.zst openshell-sandbox.zst; do
             test -s "target/vm-runtime-compressed-macos/${file}"
           done
 

.github/workflows/release-vm-kernel.yml

@@ -237,9 +237,9 @@ jobs:
 
             ### Kernel Runtime Artifacts
 
-            Pre-built kernel runtime (libkrunfw + libkrun + gvproxy) for embedding into
-            the `openshell-driver-vm` binary. These are rebuilt on demand when the kernel
-            config or pinned dependency versions change.
+            Pre-built kernel runtime (libkrunfw + libkrun + gvproxy + umoci) for embedding
+            into the `openshell-driver-vm` binary. These are rebuilt on demand when the
+            kernel config or pinned dependency versions change.
 
             | Platform | Artifact |
             |----------|----------|

.markdownlint-cli2.jsonc

@@ -1,14 +1,24 @@
 {
   "globs": [
-    "**/*.md",
-    "**/*.mdx"
+    "*.md",
+    "architecture/**/*.md",
+    "crates/**/*.md",
+    "deploy/**/*.md",
+    "docs/**/*.md",
+    "docs/**/*.mdx",
+    "e2e/**/*.md",
+    "examples/**/*.md",
+    "rfc/**/*.md"
   ],
-  "gitignore": true,
+  "gitignore": false,
   "ignores": [
     ".agents/**",
     ".claude/**",
     ".opencode/**",
     ".github/**",
+    "**/node_modules/**",
+    "target/**",
+    ".pytest_cache/**",
     "THIRD-PARTY-NOTICES/**",
     "CLAUDE.md",
     // Man page sources use pandoc markdown with multiple H1 sections

architecture/compute-runtimes.md

@@ -16,14 +16,20 @@ Each runtime receives a sandbox spec from the gateway and is responsible for:
 - Reporting lifecycle and platform events back to the gateway.
 - Cleaning up runtime-owned resources.
 
+Drivers own runtime-specific platform event interpretation. When an event should
+drive client provisioning UI, the driver attaches the shared
+`openshell.progress.*` metadata defined in `openshell-core` instead of requiring
+clients to parse Kubernetes reasons, VM cache states, or other driver-local
+reason strings.
+
 ## Runtime Summary
 
 | Runtime | Best fit | Sandbox boundary | Notes |
 |---|---|---|---|
 | Docker | Local development with Docker available. | Container plus nested sandbox namespace. | Uses host networking so loopback gateway endpoints work from the supervisor. |
 | Podman | Rootless or single-machine deployments. | Container plus nested sandbox namespace. | Uses the Podman REST API, OCI image volumes, and CDI GPU devices when available. |
 | Kubernetes | Cluster deployment through Helm. | Pod plus nested sandbox namespace. | Uses Kubernetes API objects, service accounts, secrets, PVC-backed workspace storage, and GPU resources. |
-| VM | Experimental microVM isolation. | Per-sandbox libkrun VM. | Gateway spawns `openshell-driver-vm` as a subprocess over a private, state-local Unix socket. |
+| VM | Experimental microVM isolation. | Per-sandbox libkrun VM. | Gateway spawns `openshell-driver-vm` as a subprocess over a private, state-local Unix socket. The VM driver boots a cached bootstrap `rootfs.ext4`, prepares requested OCI images inside a bootstrap VM with `umoci`, attaches the prepared image disk read-only, and gives each sandbox a writable `overlay.ext4` for merged-root changes and runtime material. |
 
 Per-sandbox CPU and memory values currently enter the driver layer through
 template resource limits. Docker and Podman apply them as runtime limits.