feat: tool definition manifest system (PR 1)

- Add ToolDefinitionManifest model with base image versioning
- Add manifest compiler: Dockerfile + Compose generation from JSON manifests
- Add permission fixer: post-start chown/chmod for mount policies
- Add tool definition CRUD API with live compile preview endpoint
- Integrate manifest-based startup flow in start_instance
- Add Alembic migration with data conversion for pi-agent
- Add 48 unit tests for manifest compiler, permission fixer, docker service
- Keep backward compatibility with legacy dockerfile_template/compose_template

Migration: applied successfully. Pi-agent converted to manifest.
Quality gates: pytest (146 passed, 4 pre-existing unrelated failures)

apps/api/tests/unit/test_permission_fixer.py

@@ -0,0 +1,145 @@
+"""Unit tests for the permission fixer."""
+
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from src.services.permission_fixer import (
+    PermissionFixError,
+    apply_mount_permissions,
+    check_root_user_available,
+    _run_in_container,
+)
+
+
+class TestApplyMountPermissions:
+    """Tests for apply_mount_permissions."""
+
+    @patch("src.services.permission_fixer._run_in_container")
+    def test_applies_chown_when_owner_declared(self, mock_run) -> None:
+        mounts = [
+            {"name": "workspace", "target": "/workspace", "owner": "user"},
+        ]
+        results = apply_mount_permissions("abc123", mounts)
+
+        assert len(results) == 1
+        assert results[0]["mount_name"] == "workspace"
+        assert results[0]["success"] is True
+        mock_run.assert_called_once()
+        args = mock_run.call_args[0]
+        assert args[0] == "abc123"
+        assert args[1] == ["chown", "-R", "user:user", "/workspace"]
+
+    @patch("src.services.permission_fixer._run_in_container")
+    def test_applies_chmod_when_mode_declared(self, mock_run) -> None:
+        mounts = [
+            {"name": "ssh", "target": "/home/user/.ssh", "mode": "0700"},
+        ]
+        results = apply_mount_permissions("abc123", mounts)
+
+        assert results[0]["success"] is True
+        # Only chmod called (no owner, so no chown)
+        assert mock_run.call_count == 1
+        chmod_call = mock_run.call_args_list[0]
+        assert chmod_call[0][1] == ["chmod", "0700", "/home/user/.ssh"]
+
+    @patch("src.services.permission_fixer._run_in_container")
+    def test_applies_file_mode_when_declared(self, mock_run) -> None:
+        mounts = [
+            {
+                "name": "ssh",
+                "target": "/home/user/.ssh",
+                "file_mode": "0600",
+            },
+        ]
+        results = apply_mount_permissions("abc123", mounts)
+
+        assert results[0]["success"] is True
+        # Only file_mode called (no owner, no mode)
+        assert mock_run.call_count == 1
+        file_mode_call = mock_run.call_args_list[0]
+        assert file_mode_call[0][1][0] == "sh"
+        assert (
+            "find /home/user/.ssh -type f -exec chmod 0600" in file_mode_call[0][1][2]
+        )
+
+    @patch("src.services.permission_fixer._run_in_container")
+    def test_skips_mount_with_no_policy(self, mock_run) -> None:
+        mounts = [
+            {"name": "workspace", "target": "/workspace", "writable": True},
+        ]
+        results = apply_mount_permissions("abc123", mounts)
+
+        assert len(results) == 1
+        assert results[0]["success"] is True
+        mock_run.assert_not_called()
+
+    @patch("src.services.permission_fixer._run_in_container")
+    def test_reports_failure_on_command_error(self, mock_run) -> None:
+        mock_run.side_effect = PermissionFixError("chown failed")
+
+        mounts = [
+            {"name": "workspace", "target": "/workspace", "owner": "user"},
+        ]
+        results = apply_mount_permissions("abc123", mounts)
+
+        assert results[0]["success"] is False
+        assert "chown failed" in results[0]["error"]
+
+    @patch("src.services.permission_fixer._run_in_container")
+    def test_stops_on_first_failure(self, mock_run) -> None:
+        """If chown fails, chmod and file_mode should not run."""
+        mock_run.side_effect = PermissionFixError("chown failed")
+
+        mounts = [
+            {
+                "name": "workspace",
+                "target": "/workspace",
+                "owner": "user",
+                "mode": "0755",
+                "file_mode": "0644",
+            },
+        ]
+        results = apply_mount_permissions("abc123", mounts)
+
+        assert results[0]["success"] is False
+        assert mock_run.call_count == 1  # Only chown attempted
+
+
+class TestRunInContainer:
+    """Tests for _run_in_container."""
+
+    @patch("subprocess.run")
+    def test_success(self, mock_run) -> None:
+        mock_run.return_value = MagicMock(returncode=0, stderr="")
+        _run_in_container("abc123", ["echo", "hello"], 10)
+        mock_run.assert_called_once()
+        cmd = mock_run.call_args[0][0]
+        assert cmd == ["docker", "exec", "--user", "root", "abc123", "echo", "hello"]
+
+    @patch("subprocess.run")
+    def test_failure_raises(self, mock_run) -> None:
+        mock_run.return_value = MagicMock(returncode=1, stderr="permission denied")
+        with pytest.raises(PermissionFixError, match="permission denied"):
+            _run_in_container("abc123", ["chown", "x"], 10)
+
+    @patch("subprocess.run")
+    def test_timeout_raises(self, mock_run) -> None:
+        import subprocess
+
+        mock_run.side_effect = subprocess.TimeoutExpired(cmd=["docker"], timeout=10)
+        with pytest.raises(PermissionFixError, match="timed out"):
+            _run_in_container("abc123", ["chown", "x"], 10)
+
+
+class TestCheckRootUserAvailable:
+    """Tests for check_root_user_available."""
+
+    @patch("src.services.permission_fixer._run_in_container")
+    def test_returns_true_when_root_exists(self, mock_run) -> None:
+        assert check_root_user_available("abc123") is True
+
+    @patch("src.services.permission_fixer._run_in_container")
+    def test_returns_false_when_root_missing(self, mock_run) -> None:
+        mock_run.side_effect = PermissionFixError("no such user")
+        assert check_root_user_available("abc123") is False