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.

core/tests/test_lifecycle.py

@@ -5,63 +5,63 @@ from __future__ import annotations
 from pathlib import Path
 from unittest.mock import patch
 
-from castle_core import lifecycle
-from castle_core.config import load_config
+from wildpc_core import lifecycle
+from wildpc_core.config import load_config
 
 
 class TestIsActive:
-    def test_service_uses_systemctl(self, castle_root: Path) -> None:
-        config = load_config(castle_root)
+    def test_service_uses_systemctl(self, wildpc_root: Path) -> None:
+        config = load_config(wildpc_root)
         with patch.object(lifecycle, "_systemctl_active", return_value=True) as mock:
             assert lifecycle.is_active("test-svc", "service", config) is True
-        mock.assert_called_once_with("castle-test-svc.service")
+        mock.assert_called_once_with("wildpc-test-svc.service")
 
-    def test_job_uses_timer(self, castle_root: Path) -> None:
-        config = load_config(castle_root)
+    def test_job_uses_timer(self, wildpc_root: Path) -> None:
+        config = load_config(wildpc_root)
         with patch.object(lifecycle, "_systemctl_active", return_value=True) as mock:
             assert lifecycle.is_active("test-job", "job", config) is True
-        mock.assert_called_once_with("castle-test-job-job.timer")
+        mock.assert_called_once_with("wildpc-test-job-job.timer")
 
-    def test_tool_checks_path(self, castle_root: Path) -> None:
-        config = load_config(castle_root)
+    def test_tool_checks_path(self, wildpc_root: Path) -> None:
+        config = load_config(wildpc_root)
         # give the tool a source so the tool branch is reachable
         config.programs["test-tool"].source = "/tmp/test-tool"
         with patch.object(lifecycle, "_on_path", return_value=True) as mock:
             assert lifecycle.is_active("test-tool", "tool", config) is True
         mock.assert_called_once_with("test-tool")
 
-    def test_unknown_is_inactive(self, castle_root: Path) -> None:
-        config = load_config(castle_root)
+    def test_unknown_is_inactive(self, wildpc_root: Path) -> None:
+        config = load_config(wildpc_root)
         assert lifecycle.is_active("does-not-exist", "service", config) is False
 
-    def test_path_deployment_checks_path(self, castle_root: Path) -> None:
+    def test_path_deployment_checks_path(self, wildpc_root: Path) -> None:
         # A `manager: path` deployment (a tool) is active when on PATH.
-        from castle_core.manifest import PathDeployment, ProgramSpec
+        from wildpc_core.manifest import PathDeployment, ProgramSpec
 
-        config = load_config(castle_root)
+        config = load_config(wildpc_root)
         config.programs["mytool"] = ProgramSpec(id="mytool", source="/tmp/mytool")
         config.tools["mytool"] = PathDeployment(manager="path", program="mytool")
         with patch.object(lifecycle, "_on_path", return_value=True) as mock:
             assert lifecycle.is_active("mytool", "tool", config) is True
         mock.assert_called_once_with("mytool")
 
-    def test_remote_deployment_is_active(self, castle_root: Path) -> None:
+    def test_remote_deployment_is_active(self, wildpc_root: Path) -> None:
         # A remote deployment has no local process; the manager is `none` → available.
-        from castle_core.manifest import RemoteDeployment
+        from wildpc_core.manifest import RemoteDeployment
 
-        config = load_config(castle_root)
+        config = load_config(wildpc_root)
         config.references["ext"] = RemoteDeployment(
             manager="none", program="ext", base_url="http://x"
         )
         assert lifecycle.is_active("ext", "reference", config) is True
 
     def test_static_deployment_active_when_dist_built(
-        self, castle_root: Path, tmp_path: Path
+        self, wildpc_root: Path, tmp_path: Path
     ) -> None:
         # A static (caddy) deployment is active once its served dir exists.
-        from castle_core.manifest import CaddyDeployment, ProgramSpec
+        from wildpc_core.manifest import CaddyDeployment, ProgramSpec
 
-        config = load_config(castle_root)
+        config = load_config(wildpc_root)
         repo = tmp_path / "fe"
         config.programs["fe"] = ProgramSpec(id="fe", source=str(repo))
         config.statics["fe"] = CaddyDeployment(