feat(debug): support /debug [nous|local] in the CLI/TUI slash command

The --nous flag was only wired into the argparse `hermes debug share`
subcommand. The /debug slash command (classic CLI + TUI, both via
process_command -> _handle_debug_command) built a hardcoded args
namespace with no `nous` attribute, so it always took the default
paste.rs path.

Pass cmd_original through to _handle_debug_command and parse an optional
destination word:

  /debug         -> public paste (default, unchanged)
  /debug nous    -> Nous-internal S3
  /debug local   -> stdout, no upload

local wins over nous (never touches the network); unknown words fall
back to the default. Add args_hint="[nous|local]" so help/autocomplete
surface it. New TestDebugSlashCommand covers the parsing + dispatch.

cli.py

@@ -8385,7 +8385,7 @@ class HermesCLI(CLIAgentSetupMixin, CLICommandsMixin):
         elif canonical == "copy":
             self._handle_copy_command(cmd_original)
         elif canonical == "debug":
-            self._handle_debug_command()
+            self._handle_debug_command(cmd_original)
         elif canonical == "update":
             if self._handle_update_command():
                 return False