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_fleet_role.py

@@ -5,8 +5,8 @@ from __future__ import annotations
 from pathlib import Path
 
 import yaml
-from castle_core.config import load_config
-from castle_core.registry import (
+from wildpc_core.config import load_config
+from wildpc_core.registry import (
     NodeConfig,
     NodeRegistry,
     load_registry,
@@ -18,7 +18,7 @@ def _write_min_config(root: Path, role: str | None) -> None:
     data: dict = {"gateway": {"port": 18000}}
     if role is not None:
         data["role"] = role
-    (root / "castle.yaml").write_text(yaml.safe_dump(data))
+    (root / "wildpc.yaml").write_text(yaml.safe_dump(data))
 
 
 def test_role_defaults_to_follower(tmp_path: Path) -> None:
@@ -32,12 +32,12 @@ def test_role_loaded_from_yaml(tmp_path: Path) -> None:
 
 
 def test_save_config_round_trips_role_and_secrets(tmp_path: Path) -> None:
-    """save_config rewrites castle.yaml from scratch — it must re-emit `role` and
+    """save_config rewrites wildpc.yaml from scratch — it must re-emit `role` and
     preserve the `secrets:` block, or a save reverts the node to a file-backend
     follower (the regression this guards)."""
-    from castle_core.config import load_config, save_config
+    from wildpc_core.config import load_config, save_config
 
-    (tmp_path / "castle.yaml").write_text(
+    (tmp_path / "wildpc.yaml").write_text(
         yaml.safe_dump(
             {
                 "gateway": {"port": 18000},
@@ -47,57 +47,57 @@ def test_save_config_round_trips_role_and_secrets(tmp_path: Path) -> None:
         )
     )
     save_config(load_config(tmp_path))
-    reloaded = yaml.safe_load((tmp_path / "castle.yaml").read_text())
+    reloaded = yaml.safe_load((tmp_path / "wildpc.yaml").read_text())
     assert reloaded.get("role") == "authority"
     assert reloaded.get("secrets", {}).get("backend") == "openbao"
 
 
 def test_save_config_preserves_arbitrary_unmanaged_global(tmp_path: Path) -> None:
     """Any top-level key save_config doesn't model must survive a rewrite."""
-    from castle_core.config import load_config, save_config
+    from wildpc_core.config import load_config, save_config
 
-    (tmp_path / "castle.yaml").write_text(
+    (tmp_path / "wildpc.yaml").write_text(
         yaml.safe_dump(
             {"gateway": {"port": 18000}, "role": "authority", "future_thing": {"x": 1}}
         )
     )
     save_config(load_config(tmp_path))
-    reloaded = yaml.safe_load((tmp_path / "castle.yaml").read_text())
+    reloaded = yaml.safe_load((tmp_path / "wildpc.yaml").read_text())
     assert reloaded.get("future_thing") == {"x": 1}
     assert reloaded.get("role") == "authority"
 
 
-def test_write_deployment_file_leaves_globals_untouched(castle_root: Path) -> None:
-    """A scoped deployment write must not rewrite castle.yaml globals (the PATCH
+def test_write_deployment_file_leaves_globals_untouched(wildpc_root: Path) -> None:
+    """A scoped deployment write must not rewrite wildpc.yaml globals (the PATCH
     guarantee that stops a deployment edit from dropping role/secrets)."""
-    from castle_core.config import load_config, write_deployment_file
+    from wildpc_core.config import load_config, write_deployment_file
 
-    cy = castle_root / "castle.yaml"
+    cy = wildpc_root / "wildpc.yaml"
     data = yaml.safe_load(cy.read_text())
     data["role"] = "authority"
     data["secrets"] = {"backend": "openbao"}
     cy.write_text(yaml.safe_dump(data))
     before = cy.read_text()
 
-    config = load_config(castle_root)
+    config = load_config(wildpc_root)
     kind, name, _dep = next(iter(config.all_deployments()))
     write_deployment_file(config, kind, name)
 
     assert cy.read_text() == before  # globals byte-identical — nothing touched them
 
 
-def test_write_program_file_leaves_globals_untouched(castle_root: Path) -> None:
-    """Scoped program write must not rewrite castle.yaml globals either."""
-    from castle_core.config import load_config, write_program_file
+def test_write_program_file_leaves_globals_untouched(wildpc_root: Path) -> None:
+    """Scoped program write must not rewrite wildpc.yaml globals either."""
+    from wildpc_core.config import load_config, write_program_file
 
-    cy = castle_root / "castle.yaml"
+    cy = wildpc_root / "wildpc.yaml"
     data = yaml.safe_load(cy.read_text())
     data["role"] = "authority"
     data["secrets"] = {"backend": "openbao"}
     cy.write_text(yaml.safe_dump(data))
     before = cy.read_text()
 
-    config = load_config(castle_root)
+    config = load_config(wildpc_root)
     name = next(iter(config.programs))
     write_program_file(config, name)