modernize re-added Vercel integrations: SDK 0.7.2, telemetry off, sibling-site wiring

- Bump vercel SDK pin 0.5.7 -> 0.7.2 (pyproject, lazy_deps) and regenerate uv.lock
- Disable the SDK's new default-on telemetry (VERCEL_TELEMETRY_DISABLED=1
  set before import, user-overridable) per the no-opt-out-telemetry policy
- Move _model_flow_ai_gateway into hermes_cli/model_setup_flows.py (god-file
  decomposition landed after the removal)
- Widen post-removal backend sets that vercel_sandbox missed: terminal_tool
  container_backend + _CONTAINER_BACKENDS, file_tools fallback set,
  env_probe._REMOTE_BACKENDS, approval._should_skip_container_guards,
  prompt_builder probe container_config
- Add terminal.vercel_runtime to config_defaults + TERMINAL_CONFIG_ENV_MAP
- Re-add vercel dependency group to nix #full variant (reverts #33773 workaround)
- Update restored tests to current contracts: upload-only credential sync-back
  (bcfc7458fa), registry-derived provider env list, parametrized backend fixture,
  drop tests superseded on main (slack wizard move #41112, nous status format)

tools/environments/vercel_sandbox.py

@@ -46,6 +46,14 @@ _DEFAULT_CONTAINER_DISK_MB = 51200
 
 def _ensure_vercel_sdk() -> None:
     """Lazy-install vercel SDK on demand. Idempotent."""
+    # The vercel SDK (>=0.7) ships default-on usage telemetry
+    # (vercel-internal-telemetry posts to telemetry.vercel.com). Hermes
+    # policy is no outbound telemetry without explicit user opt-in, so
+    # disable it before the SDK is ever imported. Users who genuinely want
+    # it can re-enable by exporting VERCEL_TELEMETRY_DISABLED=0 after this
+    # module loads — we only set the default, never override an explicit
+    # user value.
+    os.environ.setdefault("VERCEL_TELEMETRY_DISABLED", "1")
     try:
         from tools.lazy_deps import ensure as _lazy_ensure
         _lazy_ensure("terminal.vercel", prompt=False)