fix: set TERM and use login shell for interactive SSH sessions (#1754)

SSH interactive sessions ran the agent command in a non-login,
non-interactive shell — .bashrc/.profile weren't sourced and TERM
wasn't always set, making the shell feel broken (no colors, bad
line editing, missing env).

Fix for all 6 SSH-based clouds (DO, Hetzner, AWS, GCP, Fly, Daytona):
- Forward local TERM (default xterm-256color) to the remote
- Use `exec bash -l -c` for a proper login shell

Co-authored-by: Claude <claude@anthropic.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@openrouter/spawn",
-  "version": "0.6.14",
+  "version": "0.6.15",
   "type": "module",
   "bin": {
     "spawn": "cli.js"