feat(example): start DSH's folder picker on the persisted workspace (#36)

The directory picker has no start-path setting: it lists $HOME whenever it
opens. With the image default HOME=/home/node the folder explorer started on
a throwaway directory, so point HOME at the PVC-backed /workspace in both
sandbox templates. `~` and $HOME-relative tool caches/config follow; DSH_HOME
stays /home/node/.dsh, so sessions, config and credentials are unaffected.

Document the trade-off in the image contract and both examples, add
troubleshooting for sandboxes whose pod env was stamped before the change,
and assert HOME/~ in the e2e walkthrough.

Co-authored-by: SREDevOpsAgents <agents@sredevops.org>

.dsh/skills/dsh-agent-sandbox-platform/references/platform-runbook.md

@@ -125,6 +125,15 @@ kubectl -n "$NS" patch sandboxwarmpool "$POOL" --type merge -p '{"spec":{"replic
   throwaway pod, patch the policy, then resume.
 - Agent files live at `/workspace`, the same PVC mounted with
   `subPath: workspace`; it survives suspend/resume and dies with the PVC.
+- The templates set `HOME=/workspace` (the image default is `/home/node`). DSH's
+  directory picker lists `$HOME` when it opens and has no start-path setting, so
+  this is what makes the folder explorer start on the persisted workspace; `~`
+  and `$HOME`-relative tool caches/config also resolve there. `DSH_HOME` remains
+  `/home/node/.dsh`, so state and credentials stay out of the workspace. Pod env
+  is stamped at sandbox creation: a sandbox created before the override keeps
+  the old `HOME` until it is recreated (or its `podTemplate` is patched and the
+  sandbox resumed). Verify with
+  `kubectl -n "$NS" exec "$POD" -- printenv HOME`.
 - DSH confines bash with its own file sandbox (`bubblewrap`, else Landlock) and
   fails closed with `SANDBOX_UNAVAILABLE` when neither works. The image ships
   `bubblewrap`, but it is unsetuid and needs an unprivileged user namespace that

.dsh/skills/dsh-agent-sandbox-platform/references/troubleshooting.md

@@ -19,6 +19,7 @@ events, then compare desired vs observed state. Keep output bounded. Never
 | `CrashLoopBackOff`, probe 401 | logs, `describe` | Probe path is `/`; use `/favicon.svg`. |
 | Restart with mode-660 error | logs mention `.credentials.yaml` | kubelet fsGroup widened the file; suspend, `chmod 600` from a throwaway pod, patch `fsGroupChangePolicy: OnRootMismatch`, resume. |
 | Every bash command fails with `SANDBOX_UNAVAILABLE` | DSH tool result names the requested mode and backends | DSH's own command sandbox has no usable runner: `bubblewrap` ships in the image but is unsetuid and needs an unprivileged user namespace this hardened pod does not grant, and no Landlock runner is available. The example template sets `DSH_PERMISSION_MODE=danger-full-access`; do not grant capabilities to restore it unless the operator explicitly accepts that downgrade. |
+| Folder picker opens on `/home/node`, not the workspace | `kubectl exec <pod> -- printenv HOME` | The sandbox predates the template's `HOME=/workspace` and pod env is stamped at creation. Recreate the sandbox (PVC survives) or patch its `podTemplate` with `HOME`, then resume. Workspace dotfiles (`.cache`, `.config`, `.npm`, `.agents`) are the expected trade-off of the override, not a fault. |
 | PVC `Pending` | `kubectl describe pvc`, StorageClass | No default provisioner, access mode, zone binding. |
 | Launch token not found | `kubectl logs <pod> --tail=2000 | grep 'dsh web:'` | Pod not ready yet, or logs rotated. Do not guess tokens; wait for readiness. |
 | Sandbox reports `Finished=True` | pod phase, `kubectl get events` | The backing Pod reached `Failed` (eviction, spot reclaim) and `failedPodPolicy` defaults to `Retain`. Delete the Pod to force a replacement, or set `Recreate` (v1.0.8+) on the Sandbox/template; the claim and PVCs survive either way. |