feat: Add UI benchmark driver and scenarios for graph interactions

- Introduced `ui_bench_driver.mjs` to read scenarios and fixture manifest, generating a deterministic run plan.
- Created `ui_bench_plan.md` outlining the purpose, scope, and next steps for the benchmark.
- Added `ui_bench_scenarios.json` containing various scenarios for graph UI interactions.
- Implemented tests for CLI commands, ensuring bundle verification and telemetry defaults.
- Developed schemas for orchestrator components, including replay manifests and event envelopes.
- Added mock API for risk management, including listing and statistics functionalities.
- Implemented models for risk profiles and query options to support the new API.

docs/modules/cli/contracts/install-integrity.md

@@ -0,0 +1,15 @@
+# CLI Install & Update Integrity (v1) — 2025-12-01
+
+Requirements
+- Checksums: Every release publishes `stellaops-cli-$version.tar.zst` with `SHA256SUMS` + detached `.sig`.
+- Verification: `stella install` and `stella self-update` run `cosign verify` by default against pinned public key fingerprint; `--skip-verify` prohibited.
+- Offline: Provide `install-offline.sh` that reads from kit directory with checksum + signature checks only; no network fetches.
+- Buildx plugin: pin image digest (see `cli-spec-v1.yaml`); rollback command included in help.
+
+Failure modes
+- Missing checksum/signature → command fails with exit code 21 and structured error.
+- Digest mismatch → command fails with exit code 22; log path to offending file.
+
+Artifacts
+- Public key fingerprints recorded in `cli-spec-v1.yaml`.
+- Example verify script to be bundled in release kit: `scripts/cli/verify-install.sh`.