Update documentation and CLI behavior for GPU management

- Clarified the behavior of `Ctrl+C` and `Ctrl+D` in the README and other documentation, specifying that `Ctrl+C` only stops the tunnel while keeping the GPU active, and `Ctrl+D` stops the GPU while preserving disk data.
- Enhanced the CLI documentation to reflect these changes, ensuring users understand the implications of these commands during GPU operations.
- Improved the handling of data bindings and remounting logic in the codebase to prevent issues with empty model tabs in the UI.
- Added tests to validate the new command behaviors and ensure proper documentation alignment.

src/gpu_rent/access_card.py

@@ -124,6 +124,9 @@ def render_access_panel(
         cmds.add_row("открыть LLM", "gpu-rent open --llm")
     cmds.add_row("hold killer", "gpu-rent hold")
     cmds.add_row("стоп GPU", "gpu-rent stop")
+    if tunneled:
+        cmds.add_row("Ctrl+C", "туннель off, GPU жив")
+        cmds.add_row("Ctrl+D", "stop GPU, диски остаются")
     if not tunneled:
         cmds.add_row("туннель", "gpu-rent tunnel --open")
 
@@ -217,6 +220,7 @@ def print_access_card(
         for line in mcp_snippet_lines(cfg):
             log(line)
         log("hold: gpu-rent hold   |  stop: gpu-rent stop")
+        log("Ctrl+C — туннель off, GPU жив  |  Ctrl+D — stop GPU")
         log("")
         return
     from gpu_rent.term import console as default_console