CLI: add a 'castle tool' lens + sweep for model alignment

The tools lens coding assistants need. 'castle tool list [--json]' lists tools
(programs with a manager:path deployment) surfacing each tool's actual EXECUTABLE
— resolved from pyproject [project.scripts], which can differ from the program
name (litellm-intent-router → intent-router) — plus description and install state.
'castle tool info <name> [--json]' details one; 'castle tool install|uninstall'.
--json is a clean machine-readable catalog for building context.

Sweep: main.py descriptions/help mention the tool lens; 'frontend'→'static' in
install help; add.py._detect drops the dead behavior return (add adopts source
only); stale comments/help fixed. Docs (CLAUDE.md/README/registry) document
'castle tool'. Tests: cli/tests/test_tool.py (list/info/json).

Suites: core 124, cli 29, castle-api 58.

cli/tests/test_tool.py

@@ -0,0 +1,60 @@
+"""Tests for the `castle tool` lens."""
+
+from __future__ import annotations
+
+import json
+from argparse import Namespace
+from pathlib import Path
+from unittest.mock import patch
+
+
+def _config(castle_root: Path):
+    from castle_cli.config import load_config
+
+    return load_config(castle_root)
+
+
+class TestToolList:
+    def test_list_includes_tool(self, castle_root: Path, capsys: object) -> None:
+        with patch("castle_cli.commands.tool.load_config", return_value=_config(castle_root)):
+            from castle_cli.commands.tool import run_tool_list
+
+            rc = run_tool_list(Namespace(json=False))
+        assert rc == 0
+        out = capsys.readouterr().out  # type: ignore[attr-defined]
+        assert "test-tool" in out
+        # test-svc is a service (systemd), not a tool — must not appear.
+        assert "test-svc" not in out
+
+    def test_list_json_payload(self, castle_root: Path, capsys: object) -> None:
+        with patch("castle_cli.commands.tool.load_config", return_value=_config(castle_root)):
+            from castle_cli.commands.tool import run_tool_list
+
+            rc = run_tool_list(Namespace(json=True))
+        assert rc == 0
+        data = json.loads(capsys.readouterr().out)  # type: ignore[attr-defined]
+        tool = next(t for t in data if t["name"] == "test-tool")
+        # The coding-assistant context payload.
+        for key in ("name", "executables", "description", "installed", "source"):
+            assert key in tool
+        assert isinstance(tool["executables"], list) and tool["executables"]
+
+
+class TestToolInfo:
+    def test_info_json(self, castle_root: Path, capsys: object) -> None:
+        with patch("castle_cli.commands.tool.load_config", return_value=_config(castle_root)):
+            from castle_cli.commands.tool import run_tool_info
+
+            rc = run_tool_info(Namespace(name="test-tool", json=True))
+        assert rc == 0
+        data = json.loads(capsys.readouterr().out)  # type: ignore[attr-defined]
+        assert data["name"] == "test-tool"
+        assert data["executables"]
+
+    def test_info_rejects_non_tool(self, castle_root: Path, capsys: object) -> None:
+        # test-svc is a service deployment, not a tool.
+        with patch("castle_cli.commands.tool.load_config", return_value=_config(castle_root)):
+            from castle_cli.commands.tool import run_tool_info
+
+            rc = run_tool_info(Namespace(name="test-svc", json=False))
+        assert rc == 1