feat(mcpServer): probe_mcp_server looks at a URL before it is registered (CLEAN-78)

[maksymhryzodub-prog]

Jira: CLEAN-78

Why

CLEAN-109 gave the Rancher agent the MCP registry tools, but nothing could look at an endpoint first: to register https://mcp.silpo.ua/mcp the person had to know it speaks streamable HTTP and wants OAuth. The admin form also still had no oauth option.

What

API — probe_mcp_server({ url } | { id }), operator-only like the rest of the registry (api/src/slices/mcpServer/mcpProbe.tool.ts):

• McpProbeService holds the decisions: OAuth metadata on the origin first, then a handshake over streamable HTTP, SSE only when the endpoint answers 404/405; a 401 next to RFC 8414 metadata reads as authType: oauth (with dynamic-registration / PKCE / scopes), a 401 without it as bearer, a clean handshake as none plus the tool list and server name. One next line tells the model what to call.
• McpProbeConnector is the SDK half (same client transports the runtime uses), behind an interface so the service is unit-tested without a socket.
• A pasted URL passes the A2A public-address guard (a probe reports tools/list into the chat — exactly what an SSRF wants); a registered row by id skips it, since built-ins live on cluster hosts. Results never carry a credential; a stored bearer/header is sent and only its verdict comes back. Both spellings of a header credential are accepted (Header-Name: value as the runtime parses, and the JSON the form used to show).
• Contract row in specs/016-agent-tool-parity/contracts/tools.md; 21 new tests.

Admin — oauth in the auth-type select (no value field, a note on how the connect happens), the header label now shows the Header-Name: value form the runtime actually reads, and the MCP servers page points at the Rancher chat and its Tools panel. Twin-console check: app/ has no mcpServer slice, nothing to mirror.

Verification

• api: jest on mcpServer + mcp → 15 suites, 154 tests green; tsc --noEmit clean; eslint clean on the new files.
• admin: npx nuxt typecheck clean.
• Not exercised against the live Silpo endpoint from this machine. Smoke test in the Rancher chat: "Check what the MCP server at https://mcp.silpo.ua/mcp offers" → expect transport: streamableHttp, authType: oauth, oauth.dynamicRegistration: true, tools: null, and a next line pointing at register_mcp_server + start_mcp_oauth.

Stacked on top: #CLEAN-80 PR (per-user tokens) targets this branch.

Live test (2026-09-23, Rancher chat tools over the ranch MCP endpoint, real Silpo)

• probe_mcp_server { url: https://mcp.silpo.ua/mcp } → authType: oauth, dynamic registration + PKCE detected, tools: null, next pointing at register_mcp_server / start_mcp_oauth.
• by id on the open CleanSlice server → reachable, 4 tools, server name; a private URL is refused before any request; a built-in row on a cluster host is probed guard-free and reported unreachable honestly.
• register_mcp_server → set_template_mcps → list_agent_mcps worked as a chain for Silpo.

🤖 Generated with Claude Code

https://claude.ai/code/session_01KtJu4QscRKbDdj8WLL9aVL