chore(seidroid): remove xreview while its approach is reconsidered

.github/seidroid/README.md

@@ -9,9 +9,8 @@ publishes. The reusable *workflows* that run these features live in `.github/wor
 | Feature | What it is | Trigger |
 |---|---|---|
 | [`ai-review/`](ai-review/) | The workflow-driven seidroid[bot] helpers and their base prompts: an automatic three-pass PR review (OpenAI Codex ∥ Cursor → Claude synthesis, posting one PR review + an `AI Review` check) and the conversational `@seidroid` assistant. Prompts: `scout.md`, `review.md`, `assistant.md`. | `pull_request` (review); `@seidroid` mention (assistant) |
-| [`xreview/`](xreview/) | On-demand, sandbox-backed deep review. Drives the `sei-droid` agent inside a managed omnigent Kubernetes sandbox with a real `git`/`gh` toolchain, so it can build, test, and inspect the tree before returning one structured verdict. A reusable workflow (`.github/workflows/seidroid-xreview.yml`) plus a Python session driver. | `seidroid xreview` PR comment |
 
-The difference between the two review paths is the engine: `ai-review` passes the diff to
-models from inside the Actions runner and runs on every push; `xreview` drives a full agent
-session in a credentialed sandbox and is opt-in per PR, for when a review needs to actually
-run the code.
+`ai-review` passes the diff to models from inside the Actions runner, so it sees the change
+but never runs it. A sandbox-backed path that could build and test a PR before reviewing it
+lived here as `xreview/` and has been removed while its shape is reconsidered; see the pull
+request that removed it for what was learned.