bug: checkDewey doctor check uses HTTP GET against POST-only MCP endpoint

[yvonnedevlinrh]

Summary

checkDewey() in internal/doctor/checks.go performs an HTTP GET to the Dewey MCP endpoint (http://localhost:3333/mcp/). The MCP Streamable HTTP transport only accepts POST for JSON-RPC calls; a plain GET without SSE headers returns a non-200 status. This causes the doctor check to report a spurious warning ("Dewey returned HTTP 405") even when Dewey is healthy and running.

To Reproduce

1. Start Dewey with HTTP transport: dewey --http :3333
2. Run replicator doctor
3. Observe the Dewey check returns warn with Dewey returned HTTP 400 at http://localhost:3333/mcp/ (1ms)
4. Verify Dewey is healthy independently: send a JSON-RPC POST to http://localhost:3333/mcp/ and confirm it returns success

Expected behavior

When Dewey is running and healthy, the doctor check should report pass with "Dewey is reachable."

Root Cause

checkDewey() (internal/doctor/checks.go:98) uses client.Get(deweyURL). The Dewey MCP endpoint is served by the Go SDK's StreamableHTTPHandler, which routes by HTTP method: POST for JSON-RPC, GET for SSE session establishment, DELETE for session termination. A plain GET without the required Accept: text/event-stream header is not treated as a successful health probe.

Suggested Fix

The replicator already has a proper JSON-RPC health call in internal/memory/proxy.go:102-106:

func (c *Client) Health() error {
    _, err := c.Call("dewey_health", map[string]any{})
    return err
}

This method is not used by the doctor check.

Replace the raw HTTP GET in checkDewey() with a call to memory.NewClient(deweyURL).Health(), which sends a proper JSON-RPC POST to the dewey_health method. Update tests to use a JSON-RPC mock server instead of a simple HTTP handler.

Location

• Health check: internal/doctor/checks.go:94-126
• Existing JSON-RPC health call: internal/memory/proxy.go:102-106
• Dewey URL default: internal/config/config.go:27 (http://localhost:3333/mcp/)
• Tests: internal/doctor/checks_test.go:93-122