MCP Wizard: Embedded create pages show duplicate UI chrome

## Description

When `GatewayCreatePage` and `HTTPRouteCreatePage` are embedded in the MCP Setup Wizard, they render their own components that attempt to control the browser tab title. This creates duplicate Helmet components competing to manage the same DOM `` element.

## Current Behaviour

Both Helmets render simultaneously, causing:
- Two React components managing the same `<title>` element
- Unnecessary React work managing duplicate side-effects
- Fragile behavior dependent on render timing and react-helmet internals
- Semantic incorrectness: embedded components shouldn't control page-level metadata

## Expected Behaviour

Add `isEmbedded` prop to both create pages. When true:
- Hide Helmet (browser tab title management)
- Hide page heading (co-m-nav-title)

## Affected Files

- `src/components/mcp/MCPSetupWizard.tsx:227-238, 345-357`
- `src/components/gateway/GatewayCreatePage.tsx:1566-1582`
- `src/components/httproute/HTTPRouteCreatePage.tsx:599-612`

## Related

CodeRabbit comment in PR #734