fix(mcp): block suspicious stdio configs before probe

[teknium1]

Summary

MCP stdio configs now reject exfil-shaped commands before any probe/connect path can spawn them.

PR #46083 blocked persistence and config-loaded runtime startup, but hermes mcp add still probed a suspicious stdio command before the save-time rejection. This follow-up moves the guard ahead of probe/connect and reuses it for explicit runtime registration paths such as ACP-provided MCP servers.

Changes

• hermes_cli/mcp_config.py: validate suspicious stdio entries before cmd_mcp_add probe and inside _probe_single_server before _connect_server.
• tools/mcp_tool.py: centralize suspicious MCP filtering and apply it to both config-loaded discovery and direct register_mcp_servers() calls.
• hermes_cli/config.py: avoid the temporary validator name assignment pattern that produced type-checker warnings.
• tests/hermes_cli/test_mcp_security.py: add regressions proving dangerous entries do not reach probe, connect, or explicit runtime registration.

Validation

Check	Result
python3 -m py_compile hermes_cli/mcp_config.py tools/mcp_tool.py hermes_cli/config.py tests/hermes_cli/test_mcp_security.py	passed
scripts/run_tests.sh tests/hermes_cli/test_mcp_security.py tests/hermes_cli/test_mcp_config.py tests/hermes_cli/test_mcp_catalog.py tests/tools/test_mcp_tool.py	287 passed

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