Claude Web MCP connector strips trailing slashes from the configured server URL

### What happened?

The Claude Web MCP connector silently strips trailing slashes from the configured server URL, rewriting /mcp/ to /mcp. Per RFC 3986 these are different resources, so any server mounted under a slash path — the default in Starlette / FastAPI / Flask Blueprints — 404s.

### What did you expect to happen?

Use the URL exactly as pasted (don't strip trailing `/`).

### Steps to reproduce

1. Add an MCP server URL ending in `/mcp/` (with trailing slash).
2. Observe the connector normalizes it to `/mcp` (no trailing slash).
3. The server returns 404 because the resource path changed (RFC 3986).

### Area

MCP Connector (adding/managing servers)

### MCP Server (if applicable)

Custom server (Starlette, FastMCP)

### Error messages or logs

```shell

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### Additional context

_No response_