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_programs_commands.py

@@ -0,0 +1,34 @@
+"""Tests for the new per-program commands/repo fields on the programs API."""
+
+from fastapi.testclient import TestClient
+
+
+class TestProgramCommands:
+    def test_wired_in_program_surfaces_commands_and_repo(
+        self, client: TestClient
+    ) -> None:
+        """A stack-less adopted program exposes its declared commands + repo."""
+        resp = client.get("/programs")
+        assert resp.status_code == 200
+        progs = {p["id"]: p for p in resp.json()}
+        assert "wired-in" in progs
+        w = progs["wired-in"]
+        assert w["stack"] is None
+        assert w["repo"] == "https://github.com/someone/wired-in.git"
+        assert w["commands"]["lint"] == [["make", "lint"]]
+        assert w["commands"]["run"] == [["./bin/wired-in"]]
+
+    def test_wired_in_actions_resolved_from_commands(self, client: TestClient) -> None:
+        """available actions come from declared commands when there's no stack."""
+        resp = client.get("/programs")
+        w = next(p for p in resp.json() if p["id"] == "wired-in")
+        # declared lint/test/run + the composite check (lint/test available)
+        assert set(w["actions"]) >= {"lint", "test", "run"}
+        assert "build" not in w["actions"]  # not declared, no stack
+
+    def test_tools_via_kind_filter(self, client: TestClient) -> None:
+        """Tools are reached via /programs?kind=tool (no dedicated /tools)."""
+        resp = client.get("/programs", params={"kind": "tool"})
+        assert resp.status_code == 200
+        ids = [p["id"] for p in resp.json()]
+        assert "wired-in" in ids and "test-tool" in ids