[Repo Assist] fix(mcp): replace hardcoded 30s with defaultConnectTimeout constant, fix <= 0 guard (#3946)

🤖 *This is a Repo Assist automated pull request.*

## Summary

Closes #3933.

Two locations in `internal/mcp/connection.go` used the magic literal `30
* time.Second` for the HTTP connect-timeout fallback. A canonical
constant `config.DefaultConnectTimeout = 30` already exists in
`internal/config/config_core.go`, but importing that package into
`internal/mcp` would pull in `init()` functions with side effects.
Instead, this PR introduces a local unexported constant to be the single
source of truth within the package.

It also fixes a latent bug: `reconnectSDKTransport` guarded with `== 0`,
which left negative values through as-is. The guard is now `<= 0`,
consistent with `NewHTTPConnection`.

## Root cause

Issue #3933 (Duplicate Code Detector) identified:
- `NewHTTPConnection` (line ~202): `if connectTimeout <= 0 {
connectTimeout = 30 * time.Second }`
- `reconnectSDKTransport` (line ~386): `if timeout == 0 { timeout = 30 *
time.Second }` — note inconsistent guard

Both hardcode 30 s instead of using a named constant, and the guards
differ.

## Changes

| File | Change |
|------|--------|
| `internal/mcp/connection.go` | Add `const defaultConnectTimeout = 30 *
time.Second`; replace both magic literals with the constant; fix `== 0`
→ `<= 0` guard in `reconnectSDKTransport` |

## Trade-offs

- **Why a local constant, not importing `config`?** `internal/config`
has `init()` functions that register flags and load schemas. Importing
it into `internal/mcp` just for one constant would be a heavyweight
dependency and could cause ordering surprises. A comment on the constant
explicitly documents the sync requirement.
- **Behavioural change:** A negative `connectTimeout` passed to
`reconnectSDKTransport` previously slipped through; it now falls back to
30 s. This is the correct behaviour (negative durations are invalid) and
consistent with `NewHTTPConnection`.

## Test Status

⚠️ **Infrastructure constraint**: `proxy.golang.org` is blocked by the
environment firewall, preventing `go test` from downloading the required
Go toolchain (go1.25.0). The change is a pure constant-introduction
refactor with no logic change for valid inputs; the `== 0` → `<= 0`
guard fix is covered by the companion PR adding dedicated tests
(`repo-assist/test-connect-timeout-defaults`).




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Author: lpcox

internal/mcp/connection.go

@@ -24,6 +24,11 @@ import (
 
 var logConn = logger.New("mcp:connection")
 
+// defaultConnectTimeout is the fallback connect timeout used when the configured timeout
+// is non-positive or otherwise invalid.
+// Kept in sync with config.DefaultConnectTimeout (30 s) to avoid importing the config package.
+const defaultConnectTimeout = 30 * time.Second
+
 // ContextKey for session ID
 type ContextKey string
 
@@ -199,7 +204,7 @@ func NewConnection(ctx context.Context, serverID, command string, args []string,
 func NewHTTPConnection(ctx context.Context, serverID, url string, headers map[string]string, oidcProvider *oidc.Provider, oidcAudience string, keepAlive time.Duration, connectTimeout time.Duration) (*Connection, error) {
 	// Apply default connect timeout when not specified
 	if connectTimeout <= 0 {
-		connectTimeout = 30 * time.Second
+		connectTimeout = defaultConnectTimeout
 	}
 	logger.LogInfo("backend", "Creating HTTP MCP connection with transport fallback, url=%s, connectTimeout=%v", url, connectTimeout)
 	ctx, cancel := context.WithCancel(ctx)
@@ -379,8 +384,8 @@ func (c *Connection) reconnectSDKTransport() error {
 	}
 
 	timeout := c.connectTimeout
-	if timeout == 0 {
-		timeout = 30 * time.Second
+	if timeout <= 0 {
+		timeout = defaultConnectTimeout
 	}
 	connectCtx, cancel := context.WithTimeout(c.ctx, timeout)
 	defer cancel()