Rename Castle -> Wild PC across the repo

Repo-side rename only (Phases 1-3 of the migration plan); the live box
(~/.castle, systemd units, /data/castle, domains) is a separate cutover.

- Slug `castle` -> `wildpc`: CLI command, module names (wildpc_core/cli/api),
  dist names, entry point `wildpc = wildpc_cli.main:main`.
- Identifiers: CastleConfig/NATSClient/DirError/MDNS -> Wildpc*.
- Env/constants: CASTLE_* -> WILDPC_*; ~/.castle -> ~/.wildpc, castle.yaml ->
  wildpc.yaml, /data/castle -> /data/wildpc.
- Systemd UNIT_PREFIX castle- -> wildpc-; own programs castle-api/gateway/etc.
- Display prose "Castle" -> "Wild PC" in docs, agent-guide files, README, frontend.
- Package dirs and bootstrap yaml renamed via git mv; lockfiles regenerated;
  redundant nested uv.lock files dropped (workspace root lock is authoritative).

Tests: core 273, cli 47, wildpc-api 120 all pass. Frontend type-checks + builds.
Fixed a stale test fixture (secret_env_path kind arg) broken pre-rename.

wildpc-api/tests/test_nodes.py

@@ -0,0 +1,94 @@
+"""Tests for nodes endpoints."""
+
+from pathlib import Path
+
+from fastapi.testclient import TestClient
+
+from wildpc_core.registry import Deployment, NodeConfig, NodeRegistry
+
+from wildpc_api.mesh import MeshStateManager
+
+
+class TestNodesList:
+    """GET /nodes endpoint tests."""
+
+    def test_returns_local_node(self, client: TestClient) -> None:
+        """Always returns the local node."""
+        response = client.get("/nodes")
+        assert response.status_code == 200
+        data = response.json()
+        assert len(data) >= 1
+        local = data[0]
+        assert local["hostname"] == "test-node"
+        assert local["is_local"] is True
+        assert local["online"] is True
+
+    def test_local_node_counts(self, client: TestClient) -> None:
+        """Local node has correct deployment counts."""
+        response = client.get("/nodes")
+        data = response.json()
+        local = data[0]
+        assert local["deployed_count"] == 2  # test-svc + test-tool
+        assert local["service_count"] == 1  # only test-svc is a service
+
+    def test_includes_remote_nodes(
+        self, client: TestClient, registry_path: Path
+    ) -> None:
+        """Remote nodes from mesh state are included."""
+        import wildpc_api.mesh as mesh_mod
+
+        original = mesh_mod.mesh_state
+        try:
+            mgr = MeshStateManager()
+            remote_reg = NodeRegistry(
+                node=NodeConfig(hostname="devbox", gateway_port=9000),
+                deployed={
+                    "remote-svc": Deployment(
+                        manager="systemd",
+                        launcher="python",
+                        run_cmd=["svc"],
+                        port=9050,
+                        kind="service",
+                    ),
+                },
+            )
+            mgr.update_node("devbox", remote_reg)
+            mesh_mod.mesh_state = mgr
+
+            # Also patch the reference in the nodes module
+            import wildpc_api.nodes as nodes_mod
+
+            nodes_mod.mesh_state = mgr
+
+            response = client.get("/nodes")
+            data = response.json()
+            hostnames = [n["hostname"] for n in data]
+            assert "devbox" in hostnames
+            devbox = next(n for n in data if n["hostname"] == "devbox")
+            assert devbox["is_local"] is False
+            assert devbox["deployed_count"] == 1
+        finally:
+            mesh_mod.mesh_state = original
+            import wildpc_api.nodes as nodes_mod2
+
+            nodes_mod2.mesh_state = original
+
+
+class TestNodeDetail:
+    """GET /nodes/{hostname} endpoint tests."""
+
+    def test_local_node_detail(self, client: TestClient) -> None:
+        """Returns local node detail with deployed components."""
+        response = client.get("/nodes/test-node")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["hostname"] == "test-node"
+        assert data["is_local"] is True
+        assert len(data["deployed"]) == 2  # test-svc + test-tool
+        svc = next(d for d in data["deployed"] if d["id"] == "test-svc")
+        assert svc["node"] == "test-node"
+
+    def test_unknown_node_returns_404(self, client: TestClient) -> None:
+        """Returns 404 for unknown hostname."""
+        response = client.get("/nodes/nonexistent")
+        assert response.status_code == 404