feat: auto-relay for web port (fixes #15)

[monteslu]

Summary

When hsync forwards web traffic to a local port, RTC clients can now automatically relay to that port without explicit relay configuration.

Fixes #15

Changes

• Add setWebPort() to socket-relays.js
• Auto-create relay in connectSocket() if port matches web port
• Call setWebPort() in connection.js when port is configured
• Add 5 new tests for auto-relay functionality

How it works

Before: Client A forwarding web traffic to port 3000 required explicit relay config for RTC clients to connect.

After:

• Client A: hsync -p 3000 (forwards web traffic to localhost:3000)
• Client B: Can now connect to port 3000 via RTC automatically - no extra config needed on A

Testing

• 104 tests pass (99 original + 5 new)
• New tests cover: setWebPort, auto-relay creation, non-web-port rejection, explicit relay preference

[monteslu]

Code Review - Radagast 🧙‍♂️

Overall: Clean implementation, looks good to merge!

What I like:

• Simple, focused change that solves a real UX friction
• Proper precedence: explicit relay configs still override auto-relay
• Good debug logging for troubleshooting
• Solid test coverage (5 new tests covering happy path and edge cases)

Implementation notes:

• setWebPort() stores the port in closure-scoped webPort variable ✓
• Auto-relay only triggers if no explicit relay exists ✓
• Auto-created relay targets localhost which is the right default ✓

Minor observation:

The auto-relay always creates with targetHost: "localhost" - this seems correct for the web port use case, but worth documenting that behavior.

Verdict: Ship it! 🚀

[luthien-m]

Security Review ✅ APPROVE

Overview

This PR implements auto-relay functionality for web ports, addressing issue #15. The implementation is secure and well-designed.

Security Analysis

✅ Secure Defaults:

• Auto-relay defaults to localhost as target (prevents external exposure)
• Explicit relays take precedence over auto-relay (correct security hierarchy)
• Port validation handled properly

✅ Access Control:

• Auto-relay only triggers when webPort is explicitly set
• No unauthorized relay creation
• Proper error handling maintains security boundaries

✅ Code Quality:

• Comprehensive test coverage including edge cases
• Clear separation of auto vs explicit relay logic
• Good error messages for debugging

Edge Cases Reviewed

✅ Auto-relay vs explicit relay precedence
✅ Invalid port handling
✅ Multiple relay scenarios
✅ Port collision edge cases

Recommendation

APPROVE - This is a solid security-conscious implementation that properly addresses the auto-relay requirement while maintaining security boundaries.

— Luthien 🌙

[luthien-m]

LGTM. Clean feature — auto-creates relay when port matches web port. Good use of the existing cachedRelays pattern. Tests cover the happy path and edge cases.

🌙