[Repo Assist] fix: remove redundant log.Printf calls from connection.go (#3640)

🤖 *This PR was created by Repo Assist, an automated AI assistant.*

Addresses #3633.

## Problem

`internal/mcp/connection.go` had five `log.Printf` calls that either
duplicated adjacent `logger.LogInfo` structured-log calls or wrote to
stderr with no structured counterpart. This meant:
- Operators monitoring `mcp-gateway.log` would miss some events (e.g.
"Started MCP server")
- Operators watching stderr got duplicate lines for the same event with
slightly different wording
- The `"log"` standard-library import persisted only to serve these
calls

## Changes

| Line | Old | New |
|------|-----|-----|
| 144 | `log.Printf("Starting MCP server command: ...")` | Removed —
`logger.LogInfo` on line 143 already covers this |
| 148 | `log.Printf("Connecting to MCP server...")` | Removed —
`logConn.Print("Initiating MCP server connection and handshake")` on the
next line already covers this at debug level |
| 178 | `log.Printf("Started MCP server: ...")` | Replaced with
`logger.LogInfo("backend", "Started MCP server: ...")` — now written to
`mcp-gateway.log` |
| 241 | `log.Printf("Configured HTTP MCP server with streamable
transport: ...")` | Removed — `logger.LogInfo` on line 240 already
covers this |
| 264 | `log.Printf("Configured HTTP MCP server with plain JSON-RPC
transport: ...")` | Removed — `logger.LogInfo` on line 263 already
covers this |

The now-unused `"log"` standard-library import is also removed.

## Test Status

⚠️ **Infrastructure note**: The Go 1.25.0 toolchain required by `go.mod`
is unavailable in this environment (blocked by network firewall). All
changes are mechanical deletions of `log.Printf` calls with no logic
changes. `go vet` and `make test` will run in the GitHub Actions CI
environment where Go 1.25.0 is available.

## Trade-offs

- The "Started MCP server" event (previously only on stderr) is now in
`mcp-gateway.log`. This is strictly better — it was a gap in structured
logging.
- Removing the two "Connecting" and "Starting" stderr echoes reduces
startup noise on stderr; the events are still visible via `DEBUG=mcp:*`
through `logConn`.

Closes #3633




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Author: lpcox

internal/mcp/connection.go

@@ -7,7 +7,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"log"
 	"net/http"
 	"os/exec"
 	"strings"
@@ -141,11 +140,9 @@ func NewConnection(ctx context.Context, serverID, command string, args []string,
 	}()
 
 	logger.LogInfo("backend", "Starting MCP backend server, command=%s, args=%v", command, sanitize.SanitizeArgs(expandedArgs))
-	log.Printf("Starting MCP server command: %s %v", command, sanitize.SanitizeArgs(expandedArgs))
 	transport := &sdk.CommandTransport{Command: cmd}
 
 	// Connect to the server (this handles the initialization handshake automatically)
-	log.Printf("Connecting to MCP server...")
 	logConn.Print("Initiating MCP server connection and handshake")
 	session, err := client.Connect(ctx, transport, nil)
 	if err != nil {
@@ -175,7 +172,7 @@ func NewConnection(ctx context.Context, serverID, command string, args []string,
 		isHTTP:   false,
 	}
 
-	log.Printf("Started MCP server: %s %v", command, sanitize.SanitizeArgs(args))
+	logger.LogInfo("backend", "Started MCP server: %s %v", command, sanitize.SanitizeArgs(expandedArgs))
 	return conn, nil
 }
 
@@ -238,7 +235,6 @@ func NewHTTPConnection(ctx context.Context, serverID, url string, headers map[st
 	conn, err := tryStreamableHTTPTransport(ctx, cancel, serverID, url, headers, headerClient, keepAlive)
 	if err == nil {
 		logger.LogInfo("backend", "Successfully connected using streamable HTTP transport, url=%s", url)
-		log.Printf("Configured HTTP MCP server with streamable transport: %s", url)
 		return conn, nil
 	}
 	logConn.Printf("Streamable HTTP failed: %v", err)
@@ -261,7 +257,6 @@ func NewHTTPConnection(ctx context.Context, serverID, url string, headers map[st
 	conn, err = tryPlainJSONTransport(ctx, cancel, serverID, url, headers, headerClient)
 	if err == nil {
 		logger.LogInfo("backend", "Successfully connected using plain JSON-RPC transport, url=%s", url)
-		log.Printf("Configured HTTP MCP server with plain JSON-RPC transport: %s", url)
 		return conn, nil
 	}
 	logConn.Printf("Plain JSON-RPC transport failed: %v", err)