feat(remote): add ssh port forwarding tool

[luoye520ww]

Summary

• Adds a top-level remote_port_forward tool for SSH-bound threads.
• Opens loopback-bound SSH tunnels, waits until the local preview port is ready, supports list/close cleanup, and disposes tunnels when a thread/runtime is cleaned up.
• Keeps the feature outside delegated subagents and requires approval for production targets.

Tests

• npm.cmd --prefix kun test -- src/adapters/tool/remote-port-forward-tool.test.ts src/remote/remote-port-forward-manager.test.ts src/remote/ssh-port-forward.test.ts
• npm.cmd --prefix kun run typecheck
• npm.cmd --prefix kun run build
• git diff --check codex/p0-remote-target-core...HEAD

Stacking

• This PR is stacked on codex/p0-remote-target-core, which corresponds to feat(remote): add guarded ssh target runtime core KunAgent/Kun#811. After feat(remote): add guarded ssh target runtime core KunAgent/Kun#811 merges, this branch should be rebased/retargeted to KunAgent/Kun:develop as the official PR.