fix(mcp): preflight python module check and surface install errors

- Verify python -m module import in preflight with fix hints

- Pass env_schema defaults in health/sync; catch JSON install exceptions in UI

Co-authored-by: Cursor <cursoragent@cursor.com>

runtime/tools/mcp/env_config.py

@@ -0,0 +1,46 @@
+from __future__ import annotations
+
+from typing import Any
+
+
+def mcp_row_env_config(row: dict[str, Any]) -> tuple[list[str], dict[str, str]]:
+    """Per-server env allowlist + defaults from registry ``env_schema``."""
+    from runtime.operations.mcp_env import mcp_env_allowlist_keys
+
+    schema = row.get("env_schema") if isinstance(row.get("env_schema"), dict) else {}
+    defaults: dict[str, str] = {}
+    schema_keys: list[str] = []
+    for k, spec in schema.items():
+        key = str(k or "").strip()
+        if not key:
+            continue
+        schema_keys.append(key)
+        if isinstance(spec, dict) and spec.get("default") is not None:
+            dv = str(spec.get("default") or "").strip()
+            if dv:
+                defaults[key] = dv
+    seen: set[str] = set()
+    allowlist: list[str] = []
+    for k in [*mcp_env_allowlist_keys(), *schema_keys]:
+        if k and k not in seen:
+            seen.add(k)
+            allowlist.append(k)
+    return allowlist, defaults
+
+
+def mcp_runtime_for_row(row: dict[str, Any], *, store: Any) -> Any:
+    from runtime.tools.mcp.filesystem_argv import build_mcp_process_command
+    from runtime.tools.mcp.runtime import McpProcessRuntime
+
+    cmd = str(row.get("entry_command") or "").strip()
+    args = [str(x) for x in (row.get("entry_args") or []) if str(x).strip()]
+    allowlist, defaults = mcp_row_env_config(row)
+    return McpProcessRuntime(
+        build_mcp_process_command(cmd, args, store=store),
+        timeout_s=float(row.get("timeout_s") or 30.0),
+        env_allowlist=allowlist,
+        env_defaults=defaults,
+    )
+
+
+__all__ = ["mcp_row_env_config", "mcp_runtime_for_row"]