feat(remote): add ssh port forwarding tool

[luoye520ww]

Summary

• Adds an SSH remote port forwarding tool for remote-bound threads.
• Waits until the localhost tunnel is actually ready before returning a URL.
• Cleans up per-thread tunnels to avoid orphan SSH processes.

Changes

• Adds SSH port forward spawning and readiness probing.
• Adds a per-thread remote port forward manager.
• Adds the remote_port_forward built-in tool and wires runtime cleanup on thread resource disposal and shutdown.

Safety

• Only available for SSH remote-bound threads.
• Binds local tunnels to 127.0.0.1.
• Allows automatic local port allocation; explicit local ports must be 1024-65535.
• Requires remotePort to be 1-65535.
• Production targets require explicit approval.

Stacking / dependency

• Depends on feat(remote): wire ssh targets into runtime tools #672 (feat(remote): wire ssh targets into runtime tools).
• This PR targets KunAgent/Kun:develop as requested, so until feat(remote): wire ssh targets into runtime tools #672 merges GitHub will show the feat(remote): wire ssh targets into runtime tools #672 remote runtime/tools diff here too.
• Clean stacked comparison is available at feat(remote): add ssh port forwarding tool luoye520ww/DeepSeek-GUI#2.

Tests

• npm.cmd --prefix kun test -- src/remote/ssh-port-forward.test.ts src/remote/remote-port-forward-manager.test.ts src/adapters/tool/remote-port-forward-tool.test.ts
• npm.cmd --prefix kun run typecheck
• git diff --check

[XingYu-Zhong]

Rebased onto current develop after remote core merge and verified port-forward tests plus kun typecheck.