fix: handle non-localhost redirect_uris in saved client_info.json

[duonghan]

fix: handle non-localhost redirect_uris in saved client_info.json

Problem

When a remote MCP server (e.g., LiteLLM proxy) returns redirect_uris containing the server's own callback URL (e.g., https://mcp.example.com/callback) during OAuth dynamic client registration, mcp-remote saves this response as-is to client_info.json.

On subsequent runs:

1. findExistingClientPort() crashes with Cannot find localhost callback URI from existing client information
2. Even if it didn't crash, the SDK would use the server-assigned redirect_uri for token exchange instead of the local http://localhost:{port}/oauth/callback, causing a redirect_uri mismatch

Root Cause

Two issues in the same flow:

1. saveClientInformation() persists the full server registration response, including server-assigned redirect_uris that don't match localhost
2. findExistingClientPort() throws when no localhost URI is found in saved redirect_uris, instead of gracefully falling back
3. clientInformation() returns the saved redirect_uris as-is, which the SDK then uses for the redirect_uri parameter in token exchange requests

Fix

1. findExistingClientPort(): Return undefined instead of throwing when no localhost URI exists — triggers normal fallback to auto-selected port
2. clientInformation(): Override redirect_uris with the current this.redirectUrl (always localhost) after loading from disk

Reproduction

1. Connect to a remote MCP server that returns non-localhost redirect_uris in its registration response (e.g., LiteLLM with SSO)
2. First connection succeeds — OAuth flow uses localhost correctly
3. Restart mcp-remote — crashes with Cannot find localhost callback URI from existing client information

Testing

• All 105 existing unit tests pass
• Added 2 new tests verifying:
  • Server-assigned redirect_uris are overridden with localhost on load
  • Other fields (client_id, client_secret, scope) are preserved
• TypeScript build passes
• Manually verified with Claude Desktop connecting to LiteLLM-proxied MCP server