feat: extract openshell-policy-schema as a thin crate with no proto dependency

AGENTS.md

@@ -33,6 +33,7 @@ These pipelines connect skills into end-to-end workflows. Individual skill files
 | `crates/openshell-server/` | Gateway server | Control-plane API, sandbox lifecycle, auth boundary |
 | `crates/openshell-sandbox/` | Sandbox runtime | Container supervision, policy-enforced egress routing |
 | `crates/openshell-policy/` | Policy engine | Filesystem, network, process, and inference constraints |
+| `crates/openshell-policy-schema/` | Policy YAML schema | Dependency-light serde types and pure YAML parsing — no proto, no gRPC |
 | `crates/openshell-router/` | Privacy router | Privacy-aware LLM routing |
 | `crates/openshell-bootstrap/` | Gateway metadata | Gateway registration metadata, auth token storage, mTLS bundle storage |
 | `crates/openshell-ocsf/` | OCSF logging | OCSF v1.7.0 event types, builders, shorthand/JSONL formatters, tracing layers |

crates/openshell-policy-schema/Cargo.toml

@@ -0,0 +1,20 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+[package]
+name = "openshell-policy-schema"
+description = "YAML schema types and pure-Rust parsing for OpenShell sandbox policies"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+repository.workspace = true
+
+[dependencies]
+serde = { workspace = true }
+serde_json = { workspace = true }
+serde_yml = { workspace = true }
+miette = { workspace = true }
+
+[lints]
+workspace = true